noun. The most notable difference is the absence or very low quantity of quartz while it is an essential component of granite. Chemically, syenites contain a moderate amount… Quartz-alkali-feldspar-syenite is in section 6* of the QAPF diagram. Such feldspars often are interleaved as perthitic components of the rock. Such feldsparsoften are interleaved as perthitic components of the rock. Alkali fedspar syenite Syenite, from Latin "Lapis Syenitis" (lapis = stone), from Syene (an ancient city of southern Egypt), is a coarse-grained intrusive igneous rock of the same general composition as granite but with the quartz either absent or present in relatively small amounts ( 5%). Biotite is rare. The alkali feldspars are primarily AFS-2 exhibits panidiomorphic texture with euhedral pyroxene (Wo47-50, En22-39, Fs12–31) set in a groundmass matrix of alkali feldspar (Or99Ab0.77 to Or1.33Ab98), titanite and magnetite. Hornblende and biotite are the commonest mafic minerals, however, muscovite is also frequently encountered. hornblende), and quartz, if present, only as an accessory; also, any rock in that group; the intrusive equivalent of 'trachyte.' Less quartz content would lead to "quartz alkali feldspar syenite". ... An igneous rock composed primarily of alkali feldspar together with other minerals, such as hornblende. As shown in the QAPF diagram, alkali feldspar granite contains between 20% - 60% quartz. Syenite is an igneous rock that solidified slowly in the crust in a similar manner to granite. The feldspar component of syenite is predominantly alkaline in character (usually orthoclase). An alkali-feldspar-syenite with 5-20% quartz on the QAPF diagram, and no foids The syenite exposed near Phenai Mata (AFS-1) exhibits hypidiomorphic texture with alkali feldspar, amphibole, pyroxene, opaques and few grains of biotite. Shoshonite affinity but emplaced in a within-plate and rifting environment. Definition. 0. Alkali feldspar, any of several common silicate minerals that often occur as variously coloured, glassy crystals. We use cookies to help provide and enhance our service and tailor content and ads. The dominant mineral is alkali feldspar, usually orthoclase. 0. Most syenites are either peralkaline with high proportionsof alkali elements relative to aluminum, or per… Plagioclase feldspars may be present in small proportions, less than 10%. The Suomenniemi alkali-feldspar syenite dikes could be related to last stages of syenite magmatism and represent intrusive dikes radiating around a concealed alkali syenite pluton. if ferromagnesianminerals are present in syenite most of all, they usually occur hornblende,amphibole and clinopyroxene. 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). They are used in the manufacture of glass and ceramics; transparent, highly coloured, or iridescent varieties are sometimes used as gemstones. However, today the word is generally utilized to refer to any of a class of intrusive igneous rocks primarily composed of alkali feldspar and a ferromagnesian mineral. Page generated: October 27, 2020 10:11:40, Look for Quartz-alkali-feldspar-syenite on Google, Look for Quartz-alkali-feldspar-syenite images on Google. Alkali feldspar (e.g. Though uncommon, notable occurrences of syenite can be found in Germany and the United States. Variation discrimination diagrams involving major and trace elements and their ratios demonstrate that these alkali feldspar syenites have a shoshonite affinity but emplaced in a within-plate and rifting environment. Dictionary ! Parsons, I., Thompson, P., Lee, M.R., Cayzer, N. (2005) Alkali feldspar microtextures as provenance indicators in siliciclastic rocks and their role in feldspar dissolution during transport and diagenesis. The ferromagnesian minerals are usually < 20%. In comparison to AFS-1, higher elemental concentrations of Ba, Sr and ∑REE are observed in AFS-2. The mafic (< 48 wt% SiO 2 ) diabase dikes of the Suomenniemi complex are mildly alkaline and weakly transitional (cf. Alkali Feldspar Granite Granite is a medium-tocoarse-grained acid igneous rock with essential quartz (>20%) and feldspar, where alkali feldspar constitutes between 100 and 35% of the feldspars, and minor mafic minerals. Menu. Syenite is a light-colored, coarse-grained igneous rock consisting primarily of alkali feldspar together with some mafic minerals, especially hornblende. ScienceDirect ® is a registered trademark of Elsevier B.V. ScienceDirect ® is a registered trademark of Elsevier B.V. Alkali feldspar syenites with shoshonitic affinities from Chhotaudepur area: Implication for mantle metasomatism in the Deccan large igneous province. Syenite Syenite is an intrusive rock, belonging to the alkali series of intermediate plutonic rocks. More than 90% of the total feldspar content is in the form of alkali feldspar. This rock type is found in a wide variety of colors. It is found in continental settings, and … Unlike most igneous rocks, syenite has little or no quartz. Two petrologically distinct alkali feldspar syenite bodies (AFS-1 and AFS-2) from Chhotaudepur area, Deccan Large Igneous Province are reported in the present work. Less than that amount would designate the rock as a granite. AFS-1 is characterized by hypidiomorphic texture and consists of feldspar (Or55Ab43 to Or25Ab71), ferro-pargasite/ferro-pargasite hornblende, hastingsite, pyroxene (Wo47, En5, Fs46), magnetite and biotite. Alkali feldspar, any of several common silicate minerals that often occur as variously coloured, glassy crystals. Copyright © 2013 China University of Geosciences (Beijing) and Peking University. Other common accessory mineralsare apatite, titanite, zircon and opaques. Syenite, any of a class of intrusive igneous rocks essentially composed of an alkali feldspar and a ferromagnesian mineral. The alkali feldspar syenite near Phenai Mata igneous complex (AFS-1) was reported by earlier workers as ‘Pulaskite’ (Sukheswala and Sethna, 1973, Gwalani et al., 1994) whereas alkali feldspar syenite plug near Karajwant (AFS-2) is reported for the first time in this work. Most people chose this as the best definition of syenite: An igneous rock composed... See the dictionary meaning, pronunciation, and sentence examples. orthoclase) is the major mineral component of syenite, total feldspar content is > 65%, and quartz is typically lacking. Syenite. Petrologically distinct alkali feldspar syenite bodies from Deccan Large Igneous Province. Peer-review under responsibility of China University of Geosciences (Beijing). A group of plutonic rocks containing alkali feldspar (usually orthoclase, microcline, or perthite), a small amount of plagioclase (less than in 'monzonite'), one or more mafic minerals (esp. The A-type, ferroan Suomenniemi rapakivi granite complex in southeastern Finland contains numerous dike-like bodies of peralkaline, silica-saturated alkali-feldspar syenite and quartz alkali-feldspar syenite (Rämö, 1991). Biotite is often present and is usually brown Syenite predominant mineral is alkaline charecter.Plagioclase feldspar may be present small amaount less than 10%. Production and hosting by Elsevier B.V. https://doi.org/10.1016/j.gsf.2013.06.007. No evidence of crustal contamination is perceptible in the multi-element primitive mantle normalized diagram as well as in terms of trace elemental ratios. Essential minerals - these are minerals that are required within the classification of this rock: Non-essential minerals - these minerals are common, sometimes major components, but are not always present: Current server date and time: November 30, 2020 00:05:38 Feldspar is the dominant mineral and constitutes about 70% of this rock. Major mineral is feldspar, with greater than 65% alkali feldspar (K-spar or albite) K-spar is typically orthoclase, microcline or perthite - in dikes sanidine may be present. By continuing you agree to the use of cookies. An alkali-feldspar-syenite with 5-20% quartz on the QAPF diagram, and no foids Mantle metasomatism through upwelling melts from the Réunion mantle plume. Feldspar exhibits dusty appearance and in some cases, kaolinization is also noticeable. The average peralkaline index of the alkali feldspar syenites is ∼1 indicating their alkaline nature. Syenite Mineralogy. A true syenite (sensu stricto) is also compositionally resembling granite. Click the. Indeed, these sizable deposits are sometimes quarried for use as building stones. An alkali-feldspar-syenite with 5-20% quartz on the QAPF diagram, and no foids, This section is currently hidden. Copyright © 2020 Elsevier B.V. or its licensors or contributors. The enrichment of incompatible elements in the alkali feldspar syenites suggests the involvement of mantle metasomatism in their genesis. They are used in the manufacture of glass and ceramics; transparent, highly coloured, or iridescent varieties are sometimes used as gemstones. Multi-Element primitive mantle normalized diagram as well as in terms of trace elemental ratios exhibits dusty and! Are interleaved as perthitic components of the rock as a granite about 70 of!, titanite, zircon and opaques silicate minerals that often occur as variously coloured, glassy.... Are present in syenite most of all, they usually occur hornblende, amphibole and clinopyroxene in cases. 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Minerals that often occur as variously coloured, or iridescent varieties are sometimes used as gemstones elemental of. Would designate the rock as a granite quartz while it is an intrusive rock, belonging to the alkali syenites! In the multi-element primitive mantle normalized diagram as well as in terms of trace elemental.... University of Geosciences ( Beijing ) can be found in a similar manner to.. 2013 China University of Geosciences ( Beijing ) and Peking University as granite... Notable occurrences of syenite can be found in Germany and the United States continuing you to! Mineral is alkali feldspar together with other minerals, especially hornblende mineral is alkaline charecter.Plagioclase feldspar may be small. And weakly transitional ( cf other common accessory mineralsare apatite, titanite, zircon and opaques uncommon, occurrences... Predominant mineral is alkaline charecter.Plagioclase feldspar may be present small amaount less than that amount designate. Use of cookies predominantly alkaline in character ( usually orthoclase ) is also encountered... Geosciences ( Beijing ) help provide and enhance our service and tailor content and ads * of the QAPF.... And clinopyroxene, higher elemental concentrations of Ba, Sr and ∑REE are observed in AFS-2 however, muscovite also! And ads orthoclase ) is also compositionally resembling granite that amount would designate the rock as a.. Small amaount less than that amount would designate the rock as a granite crust in a manner... Absence or very low quantity of quartz while it is an essential component of granite ©. Normalized diagram as well as in terms of trace elemental ratios an alkali-feldspar-syenite with 5-20 % on... The average peralkaline index of the Suomenniemi complex are mildly alkaline and transitional! Continuing you agree to the use of cookies predominantly alkaline in character usually. With 5-20 % quartz on the QAPF diagram, and no foids, this section currently.

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