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). Such feldsparsoften are interleaved as perthitic components of the rock. Mantle metasomatism through upwelling melts from the Réunion mantle plume. An alkali-feldspar-syenite with 5-20% quartz on the QAPF diagram, and no foids, This section is currently hidden. Biotite is rare. Production and hosting by Elsevier B.V. https://doi.org/10.1016/j.gsf.2013.06.007. Unlike most igneous rocks, syenite has little or no quartz. 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. The feldspar component of syenite is predominantly alkaline in character (usually orthoclase). The average peralkaline index of the alkali feldspar syenites is ∼1 indicating their alkaline nature. 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. Syenite Syenite is an intrusive rock, belonging to the alkali series of intermediate plutonic rocks. Dictionary ! 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. Alkali feldspar (e.g. Copyright © 2020 Elsevier B.V. or its licensors or contributors. 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. Menu. A true syenite (sensu stricto) is also compositionally resembling granite. Shoshonite affinity but emplaced in a within-plate and rifting environment. Syenite is a light-colored, coarse-grained igneous rock consisting primarily of alkali feldspar together with some mafic minerals, especially hornblende. More than 90% of the total feldspar content is in the form of alkali feldspar. The syenite exposed near Phenai Mata (AFS-1) exhibits hypidiomorphic texture with alkali feldspar, amphibole, pyroxene, opaques and few grains of biotite. 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. The alkali feldspars are primarily This rock type is found in a wide variety of colors. Syenite, any of a class of intrusive igneous rocks essentially composed of an alkali feldspar and a ferromagnesian mineral. They are used in the manufacture of glass and ceramics; transparent, highly coloured, or iridescent varieties are sometimes used as gemstones. Other common accessory mineralsare apatite, titanite, zircon and opaques. Less than that amount would designate the rock as a granite. Alkali feldspar, any of several common silicate minerals that often occur as variously coloured, glassy crystals. 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). 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. Plagioclase feldspars may be present in small proportions, less than 10%. Syenite is an igneous rock that solidified slowly in the crust in a similar manner to granite. if ferromagnesianminerals are present in syenite most of all, they usually occur hornblende,amphibole and clinopyroxene. 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. 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. Syenite Mineralogy. Feldspar exhibits dusty appearance and in some cases, kaolinization is also noticeable. The most notable difference is the absence or very low quantity of quartz while it is an essential component of granite. 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 By continuing you agree to the use of cookies. No evidence of crustal contamination is perceptible in the multi-element primitive mantle normalized diagram as well as in terms of trace elemental ratios. The ferromagnesian minerals are usually < 20%. hornblende), and quartz, if present, only as an accessory; also, any rock in that group; the intrusive equivalent of 'trachyte.' An alkali-feldspar-syenite with 5-20% quartz on the QAPF diagram, and no foids noun. 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%). Most syenites are either peralkaline with high proportionsof alkali elements relative to aluminum, or per… Indeed, these sizable deposits are sometimes quarried for use as building stones. orthoclase) is the major mineral component of syenite, total feldspar content is > 65%, and quartz is typically lacking. Quartz-alkali-feldspar-syenite is in section 6* of the QAPF diagram. It is found in continental settings, and … 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. Most people chose this as the best definition of syenite: An igneous rock composed... See the dictionary meaning, pronunciation, and sentence examples. Feldspar is the dominant mineral and constitutes about 70% of this rock. ... 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. 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. 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. Click the. Though uncommon, notable occurrences of syenite can be found in Germany and the United States. 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. An alkali-feldspar-syenite with 5-20% quartz on the QAPF diagram, and no foids Alkali feldspar, any of several common silicate minerals that often occur as variously coloured, glassy crystals. 0. Chemically, syenites contain a moderate amount… Such feldspars often are interleaved as perthitic components of the rock. Definition. 0. Copyright © 2013 China University of Geosciences (Beijing) and Peking University. Peer-review under responsibility of China University of Geosciences (Beijing). Biotite is often present and is usually brown 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. The enrichment of incompatible elements in the alkali feldspar syenites suggests the involvement of mantle metasomatism in their genesis. Hornblende and biotite are the commonest mafic minerals, however, muscovite is also frequently encountered. We use cookies to help provide and enhance our service and tailor content and ads. Syenite. Less quartz content would lead to "quartz alkali feldspar syenite". The dominant mineral is alkali feldspar, usually orthoclase. They are used in the manufacture of glass and ceramics; transparent, highly coloured, or iridescent varieties are sometimes used as gemstones. Petrologically distinct alkali feldspar syenite bodies from Deccan Large Igneous Province. Syenite predominant mineral is alkaline charecter.Plagioclase feldspar may be present small amaount less than 10%. 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.

alkali feldspar syenite

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