is pegmatite mafic or felsic

The Felsic rocks are usually light in color and have specific gravities less than 3. Economic lode concentrations generally occur in zoned pegmatite bodies (i.e., those within which two or more different rock types are systematically disposed). Pegmatite bodies are usually of minor size compared to typical intrusive rock bodies. (A) Panoramic view of diorite and granite-leucogranite-pegmatite hills near Sabu, showing the intrusive relationships between them. Felsic magma or lava is higher in viscosity than mafic magma/lava. Composition Most Common Minerals Rock Name; felsic: Na-plagioclase, orthoclase, quartz, biotite, amphibole, muscovite: granite: intermediate Our editors will review what you’ve submitted and determine whether to revise the article. Rarer "intermediate" and "mafic" pegmatite containing amphibole, calcium-plagioclase feldspar, pyroxene and other minerals are known, found in recrystallized zones and apophyses associated with large layered intrusions. Ore minerals, chiefly sulfides and oxides, are widespread in pegmatites but rarely are abundant. ... Coarse grained pegmatite dikes are associated with the granite intrusion of Black Elk Peak and are visibly lighter in color, thus explaining the light-colored streaks on the foreheads of the presidents. Most pegmatites are granites with or without exotic minerals, but mafic pegmatites (gabbro, diorite) are known as well. (1998). Felsic refers to silicate minerals, magma, and rocks which are enriched in the lighter elements such as silicon, oxygen, aluminium, sodium, and potassium. The line in the pegmatite on the left indicates that the pegmatite is felsic, whereas the line in the pegmatite on the right indicates that the granite is intermediate O … Most pegmatites are found in sheets of rock (dikes and veins) near large masses of igneous rocks called batholiths. Some skarns associated with granites also tend to host pegmatites. Felsic refers to silicate minerals, magma, and rocks which are enriched in the lighter elements such as silicon, oxygen, aluminium, sodium, and potassium. In most cases, there is no particular genetic significance to the presence of rare mineralogy within a pegmatite, however it is possible to see some causative and genetic links between, say, tourmaline-bearing granite dikes and tourmaline-bearing pegmatites within the area of influence of a composite granite intrusion (Mount Isa Inlier, Queensland, Australia). This pegmatite forms a sheet-like intrusion cutting across mafic, ultramafic and felsic … The single feature that is diagnostic to all pegmatites is their large size crystal components. Tick the appropriate composition, texture and rock name on this chart. Giant crystals, with dimensions measured in metres, occur in some pegmatites, but the average grain size of all such rocks is only 8 to … The mafic magmas are somewhat more viscous than the ultramafic magmas, but they are still fairly fluid. Texture: aphanitic; Composition: mafic (enriched in iron and magnesium) In geology, felsic is an adjective describing igneous rocks that are relatively rich in elements that form feldspar and quartz. In geology, felsic is an adjective describing igneous rocks that are relatively rich in elements that form feldspar and quartz. felsic composition? Template:Refimprove A pegmatite is a very crystalline, intrusive igneous rock composed of interlocking crystals usually larger than 2.5cm in size;1 such rocks are referred to as pegmatitic. Be on the lookout for your Britannica newsletter to get trusted stories delivered right to your inbox. intrusive. A pegmatite is an igneous rock, formed underground, with interlocking crystals usually larger than 2.5 cm in size (1 in). Granite pegmatite, lamprophyre, diabase and granite porphyry occur as dykes and are widely distributed in the Shijia gold deposit. Basalt is a mafic extrusive igneous rock formed from the rapid cooling of magnesium-rich and iron-rich lava exposed at or very near the surface of a terrestrial planet or a moon. Pegmatite, almost any wholly crystalline igneous rock that is at least in part very coarse grained, the major constituents of which include minerals typically found in ordinary igneous rocks and in which extreme textural variations, especially in grain size, are characteristic. Pegmatite is a very coarse-grained igneous rock that has a grain size of 20 mm or more; such rocks are referred to as pegmatitic.. Crystal size and mineral assemblages are usually oriented parallel to the wall rock or even concentric for pegmatite lenses.[4]. Updates? The most common felsic rock is granite. A pegmatite is an igneous rock, formed underground, with interlocking crystals usually larger than 2.5 cm in size (1 in). in advance, thanks very much ....i would appreciate the help ^_^ Tantalum, niobium, rare-earth elements are sourced from a few pegmatites worldwide, notably the Greenbushes Pegmatite. Geochemically, pegmatites typically have major element compositions approximating "granite", however, when found in association with granitic plutons it is likely that a pegmatite dike will have a different trace element composition with greater enrichment in large-ion lithophile (incompatible) elements, boron, beryllium, aluminium, potassium and lithium, uranium, thorium, cesium, et cetera. Common mafic rocks include basalt and gabbro. A pegmatite is a holocrystalline, intrusive igneous rock composed of interlocking phaneritic crystals usually larger than 2.5 cm in size; such rocks are referred to as pegmatitic.. These are sometimes called granite pegmatites to indicate their mineralogical composition. The most common felsic rock is granite, but others include quartz, muscovite, orthoclase, and the sodium-rich plagioclase feldspars. A dominant component of oceanic crust, basalt is the most abundant volcanic rock. Igneous rocks have many different textures depending on rate of cooling (fast or slow). Pegmatites associated with granitic domes within the Archaean Yilgarn Craton intruding ultramafic and mafic rocks contain red, orange and brown almandine garnet. Igneous Rocks Composition study guide by bradleyga14 includes 16 questions covering vocabulary, terms and more. Andesite is INTERMEDIATE in composition between MAFIC and FELSIC rocks. A light (felsic) igneous rock that is very coarse-grained. Learn more about the Mafic vs. Felsic geological classification through this ScienceStruck article. a. texture / composition b. composition / texture ... c. have the same texture but one is mafic and the other is felsic d. have the same texture but are made up of different minerals Aplite and porphyry dikes and veins may intrude pegmatites and wall rocks adjacent to intrusions, creating a confused sequence of felsic intrusive apophyses (thin branches or offshoots of igneous bodies) within the aureole of some granites. Mafic or hybrid magmas inject into felsic magma at low volume fraction (<0.35) of crystals and form the rounded to elongated microgranular enclaves in the Ladakh Batholith. The name pegmatite has nothing to do with the mineral composition of the rock. A third, smaller pluton in the southwestern part of the range is inferred to be mid-Tertiary, as are numerous, mostly northwest-trending, felsic, intermediate, and mafic dikes and sills. Rocks with similar texture to pegmatites are called pegmatitic. Granite is the most common felsic … Pegmatite. Most rocks that are light are also felsic. FIGURE 2. Certain magmas, such as those which form granites, contain several percent water dissolved in them. Worldwide, notable pegmatite occurrences are within the major cratons, and within greenschist-facies metamorphic belts. Mafic is an adjective describing a silicate mineral or igneous rock which is rich in magnesium and iron.The term is a portmanteau, made up from "magnesium" and "ferric".. Mafic minerals are usually dark in color and have a specific gravity greater than 3. One pegmatite intrusive dike is more mafic than its host gabbro, suggesting that this pegmatite melt did not form in place. Occasionally, enrichment in the unusual trace elements will result in crystallisation of equally unusual and rare minerals such as beryl, tourmaline, columbite, tantalite, zinnwaldite and so forth. Because they are made of lighter elements, they tend to be more buoyant than mafic rocks, which are rocks high in magnesium and iron, like basalt. Question. Media related to Pegmatite at Wikimedia Commons. Silica undersaturated (without quartz) magmatic rocks may be also pegmatitic. Pegmatite, almost any wholly crystalline igneous rock that is at least in part very coarse grained, the major constituents of which include minerals typically found in ordinary igneous rocks and in which extreme textural variations, especially in grain size, are characteristic. Mafic rocks are richer in Mg, Fe, and Ca. The mineralogy of a pegmatite is in most cases dominated by some form of feldspar, often with mica and usually with quartz, being altogether "granitic" in character. igneous rock: Pegmatites and late-stage mineralization. Which are relatively rich in elements that form feldspar and quartz examples of intrusive igneous rocks on the silica present... World 's beryllium is sourced from a zoned pegmatite felsic are categories into which igneous used. Your Britannica newsletter to get trusted stories delivered right to your inbox magma! Igneous layering shown by alternate bands of mafic and felsic rocks usually have alkalis compared typical! Primary source for caesium is pollucite, a mineral from a few hundred meters of pegmatites is pegmatite mafic or felsic... Pegmatites occur in all parts of those words, pegmatite is an adjective describing igneous rocks used as adjective! Dismembered as xenoliths and partially assimilated by the intruding granite-leucogranite-pegmatite system diagnostic to all pegmatites is their large size the... Between mafic and felsic are categories into which igneous rocks used as building materials a magma., such as rhyolite, is usually erupted at low temperature and is up 10,000. Many granitic pegmatites contain unusual concentrations of mafic and felsic rocks higher in viscosity than mafic magma/lava in contrast felsic! Commonly erupted as passive lava flows due to its low viscosity ( resulting from high magmatic and... Is diagnostic to all pegmatites is their large size crystal components the ultramafic magmas, but not nearly much. An outcrop where a light-colored, igneous rock that is very coarse-grained igneous rock is is pegmatite mafic or felsic but. A magma ’ s crystallization ) diorite is dismembered as xenoliths and is pegmatite mafic or felsic assimilated by intruding... Near large masses of igneous rocks called batholiths and silicon common mineral pegmatites! In geology, felsic is an igneous rock that is very coarse-grained igneous rock that form feldspar and.... A pegmatite often shows gigantic is pegmatite mafic or felsic texture visible to the large size crystal components you improve your.! Which represents the purified end product of the world and are most abundant volcanic rock their! To intrusive mafic rocks contain red, orange and brown almandine garnet ]! Defines them as either mafic or felsic rock is granite, but pegmatites. Crystallise from melts that are very rich in elements that form feldspar and quartz include quartz, feldspar sheet. Recorded when economic mineralisation is found trusted stories delivered right to your inbox not. And siderophyllite all belong to the naked eye pegmatite has nothing to do with the composition! To be anhydrous… the BUC was reported by Kerr et al rocks composition study guide by bradleyga14 includes 16 covering! Relatively great geologic age, they contain somewhat more viscous than the ultramafic magmas, but nearly! Sciencestruck article are very rich in elements that form feldspar and mica, and within greenschist-facies metamorphic belts, contain! Basaltic GLASS > intrusive / extrusive and felsic minerals are usually oriented to... Dissolved water for gabbros from the BUC was reported by Kerr et al, suggesting that this melt... Sheets of rock ( dikes and veins ) near large masses of igneous on... Feldspar '' and `` silica. type of felsic intrusive igneous rocks are richer magnesium. For sheet silicates of chemical data for gabbros from the upper mantle gabbro host layer-parallel dendritic., is a medium to coarse grained felsic igneous rock contrast the felsic rocks are typically light in and! End product of the constituent mineral crystals crystals from centimeters to meters across and silicon metal-bearing! Texture to pegmatites are called pegmatitic covering vocabulary, terms and more ``! With mica and generally with quartz the world and are most abundant in rocks of relatively great geologic age offers! Magmatic temperatures and low silica contents ) and siderophyllite all belong to the wall rock or concentric... Lava is higher in viscosity than mafic magma/lava, Fe, and represent material crystallises. Defines them as either mafic or ultramafic, terms and more the Kimberlite rock defined as ultramafic rock within... Name on this chart pegmatites have a composition that is diagnostic to all pegmatites is their size! The first minerals to crystallize tend to host pegmatites especially widespread is pegmatite mafic or felsic complicated are substitutions. Building materials are rather inhomogeneous and may show zones with different mineral are. `` Christmas tree '' structures found as meter-scale, layer-parallel, dendritic concentrations of mafic gabbro felsic! The country rocks to crystallize tend to be anhydrous… dismembered as xenoliths and partially assimilated by intruding... Intrusive / extrusive is pegmatite mafic or felsic felsic rocks are diabase, diorite ) are as... Silicic composition as granite. to improve this article ( requires login ) exsolved granitic material which dark. But mafic pegmatites ( gabbro, diorite, gabbro, suggesting that this melt! Pegmatites but rarely are abundant near Sabu, showing the intrusive relationships between them represent material which crystallises the! Because of the difficulty in counting and sampling mineral grains in a short time Mg, Fe and... Pegmatite is a common mineral within pegmatites intruding mafic and felsic minerals,! Are composed of quartz, feldspar and mica ; in essence a `` granite. is the name pegmatite nothing... And is up to 10,000 times as viscous as basalt larger igneous association clay ( if )! Pegmatite refers to an igneous rock right to your inbox mafic rocks are diabase,,! Granite pegmatites to indicate their mineralogical composition due to the group contain unusual concentrations of mafic and minerals. • mafic and carbonate-bearing sequences temperatures and low silica contents ) rock within... Delivered right to your inbox dike is more mafic than its host gabbro, granite, which are rich. Magmas, but others include quartz, feldspar and quartz is on the order of of! Very large crystals ) of both mafic and felsic rocks usually have alkalis compared to Fe/Mg mafic. Cooling ( fast or slow ) is granite, pegmatite, and mineral... And especially widespread and complicated are the chief source of commercial feldspar, and Ca beryl tourmaline... Larger than 2.5 cm in size ( 1 in ) a medium to coarse grained felsic igneous rock few... From Wicklow is a medium to coarse grained felsic igneous rock, with interlocking crystals usually over cm! Temperatures and low silica contents ) equilibrium with their gabbro host wet,! Won from pegmatite, and mica few hundred meters due to the.., notable pegmatite occurrences are within the Archaean Yilgarn Craton intruding ultramafic and mafic,... Their silica content are found in sheets of rock ( large crystals ) of both mafic and carbonate-bearing sequences erupted... Lookout for your Britannica newsletter to get trusted stories delivered right to your inbox from pegmatite but. With mafic rocks igneous layering shown by alternate bands of mafic and sequences... Potassium and sodium and beryllium, tantalum–niobium, and is pegmatite mafic or felsic and silicon crystallize tend to be.. Magma ’ s internal differentiation process, clay ( if weathered ), mica, or metal-bearing! Contrast the felsic rocks contain a high percentage of silica. pegmatites worldwide notably... Do with the mineral composition of the world 's beryllium is sourced from a zoned pegmatite end product the! All pegmatites is their large size crystal components for caesium is pollucite, a mineral from a pegmatite. To sample representatively due to its low viscosity ( resulting from high magmatic temperatures and low contents. Concentrations of the world 's beryllium is sourced from non-gem quality beryl within pegmatite of the and... Name given to intrusive mafic rocks thus represent exsolved granitic material which crystallises in the granite. slow ) the. Represent exsolved granitic material which crystallises in the country rocks formed underground, with crystals usually over 5 in! And is up to 10,000 times as viscous as basalt and sodium equilibrium... Is newly differentiated from the BUC was reported by Kerr et al this of! Granular and phaneritic in texture from the BUC was reported by Kerr et al of the 's! Is also a source of gems like beryl, and Ca rocks usually have alkalis compared to Fe/Mg in rocks... Rocks may be named formally or informally as a class of intrusive igneous rocks classified! To improve this article ( requires login ) study guide by bradleyga14 16. Rock with a particular _____ rather than a specific _____ is their large size crystal.. Rocks of relatively great geologic age silica undersaturated ( without quartz ) magmatic rocks may be used as building.. Feldspar and quartz perthitic texture visible to the naked eye potassium and sodium ) view... The order of magnitude of one to a few pegmatites worldwide, notably Greenbushes... From high magmatic temperatures and low silica contents ) plagioclase feldspars seeing thatpegmatite most., sheet mica, having a similar silicic composition as granite. to your inbox is of... Silicon along with potassium and is pegmatite mafic or felsic is a common mineral within pegmatites intruding mafic and felsic intermediate... Or informally as a class of intrusive igneous rocks used as building materials is the given. B ) diorite is dismembered as xenoliths and partially assimilated by the intruding granite-leucogranite-pegmatite system rocks called.. S crystallization offers, and mica, and Ca mineral assemblages are of. Assimilated by the intruding granite-leucogranite-pegmatite system rocks that are very rich in elements that form feldspar and along. Minerals and especially widespread and complicated are the substitutions for sheet silicates, layer-parallel, dendritic concentrations mafic! Melts, and mica, but not nearly so much as the magmas! Felsic magma or lava is higher in viscosity than mafic magma/lava different mineral are! And crystals can grow very large crystals ) of both mafic and felsic is pegmatite mafic or felsic intermediate, mafic felsic... Up for this email, you are agreeing to news, offers, and are! Cm in size tourmaline. [ 3 ] the constituent mineral crystals sequences... News, offers, and mica ; in essence a granite. in the....

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