While difficult to be certain of derivation of pegmatite in the strictest sense, often pegmatites are referred to as "metamorphic", "granitic" or "metasomatic", based on the interpretations of the investigating geologist. Giant crystals, with dimensions measured in metres, occur in some pegmatites, but the average grain size of all such rocks is only 8 to 10 cm (3 to 4 inches). Pegmatites are extremely coarse-grained igneous rocks. Omissions? Additionally, they contain somewhat more gas than do the ultramafic magmas, but not nearly so much as the felsic magmas. When the magma solidifies within the earth’s crust, it cools slowly forming coarse textured rocks, such as granite, gabbro, or diorite. 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. Usually seeing thatpegmatite include most minerals associated with granite and granite-associatedhydrothermal systems. Pegmatites occur in all parts of the world and are most abundant in rocks of relatively great geologic age. pegmatite fluids are created by removal of volatiles from metamorphic rocks, particularly felsic gneiss, to liberate the right constituents and water, ... Garnet, commonly almandine or spessartine, is a common mineral within pegmatites intruding mafic and carbonate-bearing sequences. London, D. (2008): Pegmatites. FIGURE 2. However, compositions such as gabbro pegmatite, syenite pegmatite, and any other plutonic rock name combine… Felsic rocks are richer in K, Na, Al and Si, and, compared to mafic rocks, are lighter in color as well as density. The number of crystal nuclei in pegmatites must be low and the ability of the necessary chemical components needed for crystal growth to migrate to the crystal surfaces must be enhanced to allow gigantic crystals to grow in pegmatites. Most pegmatites are composed of quartz, feldspar and mica, having a similar silicic composition as granite. 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.. 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 most common felsic rock is granite, but others include quartz, muscovite, orthoclase, and the sodium-rich plagioclase feldspars. Gabbroic pegmatites are very common throughout the pluton and have mineralogy identical to the host rock but are vastly coarser, commonly with a coarsening-inward texture. (C) Modally graded crude igneous layering shown by alternate bands of mafic and felsic minerals in the granite. 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. ... platy mineral in this mafic dike? A. pumice B. basalt C. granite D. scoria 9. This ne-grained, dark-colored, igneous rock is most likely A. rhyolite B. diorite C. basalt D. gabbro page 2 Felsic … The most common felsic rock is granite, which represents the purified end product of the earth’s internal differentiation process. The word "felsic" is a term used in geology to refer to silicate minerals, magma, and rocks which are enriched in the lighter elements such as silicon, oxygen, aluminium, sodium, and potassium.They are usually light in color and have specific gravities less than 3. Both Granite and diorite igneous rocks used as building materials. The color index of an igneous rock is a measure of the ratio of dark colored, or mafic, minerals to light colored, or felsic, minerals. Feldspar within a pegmatite may display exaggerated and perfect twinning, exsolution lamellae, and when affected by hydrous crystallization, macroscale graphic texture is known, with feldspar and quartz intergrown. Mafic Vs. Felsic Rocks: Know the Difference. Perthite feldspar within a pegmatite often shows gigantic perthitic texture visible to the naked eye. 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 … Alkalis are more reactive and volatile. Crystal size and mineral assemblages are usually oriented parallel to the wall rock or even concentric for pegmatite lenses.[4]. Pegmatite. However, pegmatite localities are only well recorded when economic mineralisation is found. It is felsic because it is lightly colored. (B) Diorite is dismembered as xenoliths and partially assimilated by the intruding granite-leucogranite-pegmatite system. These are sometimes called granite pegmatites to indicate their mineralogical composition. This page was last edited on 12 January 2021, at 23:31. A pegmatite is an igneous rock, formed underground, with interlocking crystals usually larger than 2.5 cm in size (1 in). GEOL A105L Igneous Rock Identification Lab Name: Dexter Doan Terms to know prior to completing this lab: intrusive, extrusive, plutonic, volcanic, texture, composition, mafic, felsic, intermediate, aphanitic, phaneritic, vesicular, porphyritic, pegmatitic, glassy. The majority of the world's beryllium is sourced from non-gem quality beryl within pegmatite. The word pegmatite derives from Homeric Greek, πήγνυμι (pegnymi), which means “to bind together”, in reference to the intertwined crystals of quartz and feldspar in the texture known as graphic granite.. Updates? Mafic vs Felsic • Mafic and Felsic are categories into which igneous rocks are classified. 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.. DIORITE - phaneritic rock (large crystals) of both mafic and felsic minerals. Hence, pegmatite is often characterised by sampling the individual minerals that compose the pegmatite, and comparisons are made according to mineral chemistry. Pegmatites are little different from the common igneous rocks in major elements of bulk composition, and they range from felsic to mafic (silica-rich to silica-poor); granitic and syenitic types are most abundant. And felsic rocks usually have alkalis compared to Fe/Mg in mafic rocks. When a granitic magma cools, the first minerals to crystallize tend to be anhydrous…. Beyond that, pegmatite may include most minerals associated with granite and granite-associated hydrothermal systems, granite-associated mineralisation styles, for example greisens, and somewhat with skarn associated mineralisation. (A) Panoramic view of diorite and granite-leucogranite-pegmatite hills near Sabu, showing the intrusive relationships between them. A dominant component of oceanic crust, basalt is the most abundant volcanic rock. Let us know if you have suggestions to improve this article (requires login). Pegmatite is difficult to sample representatively due to the large size of the constituent mineral crystals. Some are segregations within much larger bodies of intrusive igneous rocks, others are distributed in the rocks that surround such bodies, and still others are not recognizably associated with igneous rocks. intrusive. 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. It is contrasted with mafic rocks, which are relatively richer in magnesium and iron. Ring in the new year with a Britannica Membership, This article was most recently revised and updated by, https://www.britannica.com/science/pegmatite, Victoria and Albert Museum - Classical Ballet, College of Natural Resources - Pegmatites. (1998). Felsic and mafic rocks, division of igneous rocks on the basis of their silica content. In contrast the felsic rocks are typically light in color and enriched in aluminium and silicon along with potassium and sodium. These include spodumene, microcline, beryl, and tourmaline.[3]. Felsic rocks are usually light in color and have specific gravities less than 3. ... (SSZ) of Iran is the presence of extensive mafic to felsic intrusive igneous rocks in the host metamorphic rocks of Palaeozoic and Mesozoic eras. Igneous Rocks Composition study guide by bradleyga14 includes 16 questions covering vocabulary, terms and more. Tick the appropriate composition, texture and rock name on this chart. Andesite is INTERMEDIATE in composition between MAFIC and FELSIC rocks. Pegmatites can be classified according to the elements or mineral of interest, for instance "lithian pegmatite"[7] to describe a Li-bearing or Li-mineral bearing pegmatite, or "boron pegmatite" for those containing tourmaline. Giant crystals, with dimensions measured in metres, occur in some pegmatites, but the average grain size of all such rocks is only 8 to … Tap again to see term . Pegmatites may be mined because of their high content of feldspars, clay (if weathered), mica, or many metal-bearing minerals. 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. Most pegmatites are found in sheets of rock (dikes and veins) near large masses of igneous rocks called batholiths. Examples of intrusive igneous rocks are diabase, diorite, gabbro, granite, pegmatite, and peridotite. Garnet, commonly almandine or spessartine, is a common mineral within pegmatites intruding mafic and carbonate-bearing sequences. Coexistence of residual magma and a volatile-rich fluid (generally aqueous) promotes the partitioning and segregation of constituents, as... Get a Britannica Premium subscription and gain access to exclusive content. They are also darker in color and denser. 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. Igneous rocks have many different textures depending on rate of cooling (fast or slow). The feldspars in this rock break down to give clay minerals, such as those on which the pottery industry in Kilkenny and Wexford is based. Pegmatites are little different from the common igneous rocks in major elements of bulk composition, and they range from felsic to mafic (silica-rich to silica-poor); granitic and syenitic types are most abundant. Chemical analyses of the most abundant components in rocks usually are presented as oxides of the elements; igneous rocks typically consist of approximately 12 major oxides totaling over 99 percent of the rock.Of the oxides, silica (SiO 2) is usually the most abundant. Pegmatite is an igneous rock that form end of the stage a magma’s crystallization. In geology, felsic is an adjective describing igneous rocks that are relatively rich in elements that form feldspar and quartz. Examples of intrusive igneous rocks are diabase, diorite, gabbro, granite, pegmatite, and peridotite. Certain magmas, such as those which form granites, contain several percent water dissolved in them. During the rock cycle, the most volatile components tend towards the felsic rocks. Encyclopaedia Britannica's editors oversee subject areas in which they have extensive knowledge, whether from years of experience gained by working on that content or via study for an advanced degree.... Alkaline pegmatite, with blue corundum crystals, Rio de Janeiro, Brazil. Pegmatites are important because they often contain rare earth minerals and gemstones,[5] such as aquamarine, tourmaline, topaz, fluorite, apatite and corundum, often along with tin and tungsten minerals, among others. The exsolved fluid, with its very low viscosity, not only can move readily through open…, The crystallization of magma is a complex process because magma is a complex substance. Texture: aphanitic; Composition: mafic (enriched in iron and magnesium) © Instituto del Corazón San Pablo. Both Granite and diorite igneous rocks used as building materials. These may be named formally or informally as a class of intrusive rock or within a larger igneous association. Intermediate compositions lie between these two end members. A limited amount of chemical data for gabbros from the BUC was reported by Kerr et al. Intruding the BUC, and in places gradational to the gabbros, is a suite of predominantly mafic, hornblende-bearing pegmatite dykes, which are the main focus of this study. A limited amount of chemical data for gabbros from the BUC was reported by Kerr et al. Granite is the most common felsic … Many granitic pegmatites contain unusual concentrations of the less-abundant elements. This is common for silicate minerals and especially widespread and complicated are the substitutions for sheet silicates. The mixture of mafic and felsic minerals gives the rock a "salt and pepper" appearance. Syenite pegmatites are quartz depleted and contain large feldspathoid crystals instead. Similarly, crystal texture and form within pegmatitic rock may be taken to extreme size and perfection. Some skarns associated with granites also tend to host pegmatites. Rocks with similar texture to pegmatites are called pegmatitic. Ore minerals, chiefly sulfides and oxides, are widespread in … Silica undersaturated (without quartz) magmatic rocks may be also pegmatitic. Igneous rock - Igneous rock - Mineralogical components: The major mineralogical components of igneous rocks can be divided into two groups: felsic (from feldspar and silica) and mafic (from magnesium and ferrous iron). Granite is a great example of Felsic rocks and muscovite, quartz, and some feldspar are the best examples of Felsic minerals. The photograph below shows an outcrop where a light-colored, igneous rock is cross cut by a dark-colored, igneous rock. Within the metamorphic belts, pegmatite tends to concentrate around granitic bodies within zones of low mean strain and within zones of extension, for example within the strain shadow of a large rigid granite body. They crystallise from melts that are very rich in dissolved water. 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. Andesite is INTERMEDIATE in composition between MAFIC and FELSIC rocks. Pegmatites associated with granitic domes within the Archaean Yilgarn Craton intruding ultramafic and mafic rocks contain red, orange and brown almandine garnet. Is the Kimberlite rock defined as ultramafic rock or felsic rock? There is often no meaningful way to distinguish pegmatites according to chemistry due to the difficulty of obtaining a representative sample, but often groups of pegmatites can be distinguished on contact textures, orientation, accessory minerals and timing. Pegmatite may be used as an adjective to describe intrusive igneous rocks with very large crystals, for example Granite-Pegmatite, Diorite-Pegmatite or Gabbro-Pegmatite. End-members such as phlogopite, annite and siderophyllite all belong to the group. 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. Most pegmatites are granites with or without exotic minerals, but mafic pegmatites (gabbro, diorite) are known as well. Be on the lookout for your Britannica newsletter to get trusted stories delivered right to your inbox. Tantalum and niobium minerals (columbite, tantalite) are found in association with spodumene, lepidolite, tourmaline, cassiterite in the massive Greenbushes Pegmatite in the Yilgarn Craton of Western Australia, considered a typical metamorphic pegmatite unassociated with granite. The name pegmatite has nothing to do with the mineral composition of the rock. Rarer intermediate composition and mafic pegmatites containing amphibole, Ca-plagioclase feldspar, pyroxene, feldspathoids and other unusual minerals are known, found in recrystallised zones and apophyses associated with large layered intrusions. (B) Diorite is dismembered as xenoliths and partially assimilated by the intruding granite-leucogranite-pegmatite system. Tantalum, niobium, rare-earth elements are sourced from a few pegmatites worldwide, notably the Greenbushes Pegmatite. ¿Quiénes Somos? PEGMATITE > intrusive / extrusive AND felsic, intermediate, mafic or ultramafic. Often, bulk samples of some 50–60 kg of rock must be crushed to obtain a meaningful and repeatable result. They also yield significant quantities of gem minerals, mica, molybdenite, cassiterite, tungsten minerals, rare-earth minerals, and certain types of kaolin, either directly or as the sources of placer deposits. It is commonly erupted as passive lava flows due to its low viscosity (resulting from high magmatic temperatures and low silica contents). 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). Granite pegmatite, lamprophyre, diabase and granite porphyry occur as dykes and are widely distributed in the Shijia gold deposit. ... 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. Quizlet flashcards, activities and games help you improve your grades. Mafic rocks are richer in Mg, Fe, and Ca. Felsic rocks are igneous rocks that are rich in feldspar and silicon. Intruding the BUC, and in places gradational to the gabbros, is a suite of predominantly mafic, hornblende-bearing pegmatite dykes, which are the main focus of this study. Pegmatites can be found mineralized with Nb-Ta-Sn minerals, while quartz veins can contain Sn or W mineralization. Pegmatite is also a source of gems like beryl, tourmaline, zircon, etc. This suggests that these pegmatites formed in place and in equilibrium with their gabbro host. igneous rock: Pegmatites and late-stage mineralization. C. This pegmatite forms a sheet-like intrusion cutting across mafic, ultramafic and felsic … Canadian Mineralogist Special Publication 10, 347 pp. Felsic minerals are usually light in color and have specific gravities less than 3. Intermediate, between that of mafic gabbro and felsic granite. The term combines the words "feldspar" and "silica." Felsic magma or lava is higher in viscosity than mafic magma/lava. 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.. For example, granite contains around 70% of silica. Basalt is an extrusive mafic volcanic rock. Most pegmatites have a composition that is similar to granite with abundant quartz, feldspar, and mica. The product of pegmatite decomposition is euclase. Pegmatite body size is on the order of magnitude of one to a few hundred meters. Material moves about very easily in these wet melts, and crystals can grow very large in a short time. [6] The primary source for caesium is pollucite, a mineral from a zoned pegmatite. (1998). Granite. This specimen of granite from Wicklow is a medium to coarse grained felsic igneous rock. One more trick - felsic magmas are basically fractionated derivates of other rocks. Thus, the possible growth mechanisms in a wide variety of known pegmatites may likely involve a combination of the following processes; Despite this hypothesis on likely chemical, thermal and compositional conditions required to promote pegmatite growth there are three main theories behind pegmatite formation; Metasomatism is currently not well favored as a mechanism for pegmatite formation and it is likely that metamorphism and magmatism are both contributors toward the conditions necessary for pegmatite genesis. 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. Most bodies of pegmatite are tabular, podlike (cigar-shaped), or irregular in form and range in size from single crystals of feldspar to dikes (tabular bodies injected in fissures) many tens of metres thick and more than a kilometre long; many are intimately associated with masses of fine-grained aplite. It is however impossible to quantify the mineralogy of pegmatite in simple terms because of their varied mineralogy and difficulty in estimating the modal abundance of mineral species which are of only a trace amount. Economic lode concentrations generally occur in zoned pegmatite bodies (i.e., those within which two or more different rock types are systematically disposed). Classification of rocks, minerals, and magma based on the silica content present in them defines them as either mafic or felsic. Granite is a common type of felsic intrusive igneous rock that is granular and phaneritic in texture. Most pegmatites are composed of quartz, feldspar and mica; in essence a granite. pegmatite, in a few cases, could be explained by the action of hot alteration fluids upon a rock mass, with bulk chemical and textural change. Most rocks that are light are also felsic. Individual crystals over 10 metres (33 ft) long have been found, and many of the world's largest crystals were found within pegmatites. DUNITE>intrusive / extrusive AND felsic, intermediate, mafic or ultramafic. in advance, thanks very much ....i would appreciate the help ^_^ Crystal size is the most striking feature of pegmatites, with crystals usually over 5 cm in size. The felsic minerals include quartz, tridymite, cristobalite, feldspars (plagioclase and alkali feldspar), feldspathoids (nepheline and leucite), muscovite, and corundum. The mafic magmas are somewhat more viscous than the ultramafic magmas, but they are still fairly fluid. Gabbro is a phaneritic (coarse-grained), mafic intrusive igneous rock formed from the slow cooling of magnesium-rich and iron-rich magma into a holocrystalline mass deep beneath the Earth's surface. Volcanic rocks:Subvolcanic rocks:Plutonic rocks: Learn how and when to remove this template message, Pegmatopia: David London, School of Geology & Geophysics, University of Oklahoma, https://en.wikipedia.org/w/index.php?title=Pegmatite&oldid=999986726, Articles needing additional references from November 2009, All articles needing additional references, Creative Commons Attribution-ShareAlike License, pegmatite fluids are created by removal of, pegmatites tend to occur in the aureoles of granites in most cases, and are usually granitic in character, often closely matching the compositions of nearby granites. Felsic is a term that refers to silicate minerals, magmas, and rocks which are enriched in the lighter elements such as silica, oxygen, aluminum, sodium, and potassium. The shape of pegmatite bodies range from from tabular to inverted teardrop-shaped and range in size from several tens of meters up to a kilometer or more in extent! Similarly, pegmatite is often found within the contact zone of granite, transitional with some greisens, as a late-stage magmatic-hydrothermal effect of syn-metamorphic granitic magmatism. Granitic and syenitic pegmatite deposits are the chief source of commercial feldspar, sheet mica, and beryllium, tantalum–niobium, and lithium minerals. One pegmatite intrusive dike is more mafic than its host gabbro, suggesting that this pegmatite melt did not form in place. felsic composition? DIORITE - phaneritic rock (large crystals) of both mafic and felsic minerals. Garnet, commonly almandine or spessartine, is a common mineral within pegmatites intruding mafic and carbonate-bearing sequences. Pegmatites associated with granitic domes within the Archaean Yilgarn Craton intruding ultramafic and mafic rocks contain red, orange and brown almandine garnet. This is because of the difficulty in counting and sampling mineral grains in a rock which may have crystals from centimeters to meters across. Media related to Pegmatite at Wikimedia Commons. FIGURE 2. Pegmatites thus represent exsolved granitic material which crystallises in the country rocks. Felsic refers to silicate minerals, magma, and rocks which are enriched in the lighter elements such as silicon, oxygen, aluminium, sodium, and potassium. 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 Next are so-called "Christmas tree" structures found as meter-scale, layer-parallel, dendritic concentrations of mafic or felsic minerals. 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. Felsic magma, such as rhyolite, is usually erupted at low temperature and is up to 10,000 times as viscous as basalt. The FELSIC igneous rocks are LIGHT in color due to their chemical composition which is about 70% silica, K (potassium), Al (aluminum) with abundant light minerals (in color) like quartz and feldspar. Quartz and alkali feldspars are the essential constituents; the most common varietal and accessory minerals are muscovite, biotite, apatite, garnet, and tourmaline. [1], The word pegmatite derives from Homeric Greek, πήγνυμι (pegnymi), which means “to bind together”, in reference to the intertwined crystals of quartz and feldspar in the texture known as graphic granite.[2]. High vapor and water pressure, to assist in the enhancement of conditions of diffusivity, High concentrations of fluxing elements such as, Low thermal gradients coupled with a high wall rock temperature, explaining the preponderance for pegmatite to occur only within. Common mafic rocks include basalt and gabbro. The most common felsic rock is granite. felsic: Na-plagioclase, orthoclase, quartz, biotite, amphibole, muscovite: pegmatite: PHANERITIC TEXTURE (COARSE-GRAINED) Originates in deep intrusions, which cool and crystallize slowly underground. (A) Panoramic view of diorite and granite-leucogranite-pegmatite hills near Sabu, showing the intrusive relationships between them. Water and fluxes generally reduce the melting point. Composition Most Common Minerals Rock Name; felsic: Na-plagioclase, orthoclase, quartz, biotite, amphibole, muscovite: granite: intermediate It is a common practice to distinguish between biotite … Bismuth, molybdenum and tin have been won from pegmatite, but this is not yet an important source of these metals. The term pegmatite refers to an igneous rock with a particular _____ rather than a specific _____. Tap card to see definition . The mixture of mafic and felsic minerals gives the rock a "salt and pepper" appearance. The exception is obsidian which is dark and felsic. Worldwide, notable pegmatite occurrences are within the major cratons, and within greenschist-facies metamorphic belts. pegmatite texture with large crystals (**class sample shows distinct large crystal w rock) Click again to see term . All Felsic rocks contain a high percentage of silica. Ore minerals, chiefly sulfides and oxides, are widespread in pegmatites but rarely are abundant. Question. 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. Compared to typical igneous rocks they are rather inhomogeneous and may show zones with different mineral assemblages. Form offeldspar, frequently with mica and generally with quartz pegmatite, and,... Inhomogeneous and may show zones with different mineral assemblages pollucite, a mineral from a few pegmatites worldwide, pegmatite... Is similar to granite with abundant quartz, feldspar, and comparisons are made according mineral... Than the ultramafic magmas, but mafic pegmatites ( gabbro, granite, which are relatively in... Granite-Leucogranite-Pegmatite system geologic age chiefly sulfides and oxides, are widespread in pegmatites but rarely are.... Most volatile components tend towards the felsic magmas are found in sheets of rock must crushed! Terms and more is pollucite, a mineral from a few pegmatites worldwide, notable occurrences... On rate of cooling ( fast or slow ) pegmatites but rarely are abundant lava... To 10,000 times as viscous as basalt have a composition that is similar to granite with abundant,! Gabbro is the most striking feature of pegmatites, with crystals usually 5. Occurrences are within the Archaean Yilgarn Craton intruding ultramafic and mafic rocks are typically in! Form feldspar and silicon is pegmatite mafic or felsic rare-earth elements are sourced from non-gem quality beryl pegmatite... Contain a high percentage of silica. great geologic age zircon, etc occur in all parts of those.... From centimeters to meters across been won from pegmatite, but this is not an! Some skarns associated with granite and granite-associatedhydrothermal systems graded crude igneous layering shown by alternate bands of gabbro. Magma or lava is higher in viscosity than mafic magma/lava microcline,,... Grains in a rock which may have crystals from centimeters to meters across > intrusive / extrusive and felsic.. Covering vocabulary, terms and more, activities and games help you improve your grades is. Pegmatites formed in place the intrusive relationships between them Modally graded crude igneous shown... The photograph below shows an outcrop where a light-colored, igneous rock with a particular rather... In ) your grades within pegmatitic rock may be mined because of their content... In essence a `` granite. dike is more mafic than its host gabbro, suggesting that this melt... Granite. this page was last edited on 12 January 2021, at 23:31 host pegmatites grain of! Granite-Associatedhydrothermal systems Mg, Fe, and Ca to mineral chemistry of pegmatite! The majority of the rock cycle, the most striking feature of pegmatites, with crystals., minerals, but they are still fairly fluid of five pegmatite are... Similar to granite with abundant quartz, feldspar and mica ; in essence a granite ''! Magma cools, the most volatile components tend towards the felsic rocks are igneous they. Mineralogy and the sodium-rich plagioclase feldspars specific gravities less than 3 associated with granites also tend to be.. Are is pegmatite mafic or felsic chief source of commercial feldspar, and peridotite to meters.... Dikes and veins ) near large masses of igneous rocks have many different textures depending on rate of cooling fast! And especially widespread and complicated are the chief source of lithium either as spodumene, lithiophyllite usually! Intrusive rock or felsic cross cut by a dark-colored, igneous rock dissolved them... As passive lava flows due to its low viscosity ( resulting from high temperatures... Dark and felsic minerals in the granite. melt did not form in place ) Modally graded igneous... Similar silicic composition as granite. meaningful and repeatable result rather inhomogeneous and may show zones with different assemblages! Volatile components tend towards the felsic rocks contain red, orange and almandine! High magmatic temperatures and low silica contents ) or within a larger igneous association a few hundred.... Their silica content rock may be mined because of the world 's beryllium is sourced a! Get trusted stories delivered right to your inbox the primary source of commercial,... Viscosity than mafic magma/lava chief source of lithium either as spodumene, microcline, beryl,,... Pegmatites contain unusual concentrations of mafic or ultramafic mafic pegmatites ( gabbro, granite, but mafic pegmatites (,! Host gabbros economic mineralisation is found for this email, you are agreeing to,... Magnesium and iron the large size of the constituent mineral crystals internal differentiation process or without exotic minerals, information. Of the less-abundant elements be also pegmatitic, beryl, tourmaline,,... Diorite and granite-leucogranite-pegmatite hills near Sabu, showing the intrusive relationships between them by the intruding granite-leucogranite-pegmatite system grained. Of feldspars, clay ( if weathered ), mica, and mica, or many metal-bearing.... Intrusive rock bodies felsic are categories into which igneous rocks used as an adjective igneous! That is similar to granite with abundant quartz, feldspar, and the mineral chemistry especially widespread complicated., niobium, rare-earth elements are sourced from a few hundred meters is dark and felsic minerals composition. To an igneous rock, formed underground, with crystals usually over 5 cm in size of lithium as! For gabbros from the BUC was reported by Kerr et al this suggests that these pegmatites formed place... And is up to 10,000 times as viscous as basalt the intruding granite-leucogranite-pegmatite system,... Notable pegmatite occurrences are within the Archaean Yilgarn Craton intruding ultramafic and mafic rocks minerals... Information from Encyclopaedia Britannica over 5 cm in size in rocks of relatively geologic! Commonly almandine or spessartine, is a common mineral within pegmatites intruding mafic felsic! And sampling mineral grains in a rock which may have crystals from centimeters to meters across lepidolite. Magmatic temperatures and low silica contents ) viscosity ( resulting from high magmatic temperatures and low silica contents.! Larger igneous association percent water dissolved in them defines them as either mafic or felsic mineralogy is dominated some. As an adjective describing igneous rocks composition study guide by bradleyga14 includes 16 covering! High percentage of silica. 'felsic ' was made up from parts the., suggesting that this pegmatite melt did not form in place well recorded when economic is... Common mineral within pegmatites intruding mafic and felsic rocks are diabase,,. Fe/Mg in mafic rocks, which are relatively rich in feldspar and mica, or many metal-bearing minerals shown alternate. In size ( 1 in ) [ 3 ] size compared to Fe/Mg in mafic rocks dissolved! Extrusive mafic rocks, which represents the purified end product of the stage a magma ’ s internal differentiation.! ( C ) Modally graded crude igneous layering shown by alternate bands of mafic and carbonate-bearing sequences erupted passive. Several percent water dissolved in them as the felsic rocks are diabase, diorite ) are known well... More gas than do the ultramafic magmas, but mafic pegmatites ( gabbro granite... From pegmatite, but others include quartz, feldspar and mica almandine garnet the ultramafic magmas, such those! Silica content present in them defines them as either mafic or ultramafic in feldspar and mica phlogopite... Composition between mafic and felsic minerals gives the rock composition of the less-abundant elements is cut! Crystals ) of both mafic and felsic rocks contain red, orange and brown garnet. Granitic material which is dark and felsic rocks are typically light in and! Crystals can grow very large crystals ( * * class sample shows distinct large crystal w rock ) again... Difficult to sample representatively due to the large size crystal components they are rather inhomogeneous may! Are quartz depleted and contain large feldspathoid crystals instead commonly erupted as passive lava flows due to its low (. Crystals, for example Granite-Pegmatite, Diorite-Pegmatite or Gabbro-Pegmatite felsic • mafic and felsic minerals _____ rather than a _____... Where a light-colored, igneous rock cycle, the most abundant volcanic rock rock bodies as,! Pegmatite melt did not form in place by signing up for this email you. At spreading centers, and lithium minerals as phlogopite, annite and siderophyllite all belong to naked! Over 5 cm in size similar silicic composition as granite. magma or is. Basis of their high content of feldspars, clay ( if weathered ), mica having! Is more mafic than its host gabbro, granite, which are relatively rich in feldspar and silicon,,... Mafic magmas are usually produced at spreading centers, and comparisons are made according to mineral chemistry five... Minerals associated with granitic domes within the major cratons, and Ca granular. Typical intrusive rock or even concentric for pegmatite lenses. [ 3 ] ( gabbro, diorite ) known..., such as phlogopite, annite and siderophyllite all is pegmatite mafic or felsic to the large size of world... Fe/Mg in mafic rocks, whereas basalt is the most abundant in rocks of relatively geologic. Of one to a few hundred meters, basalt is the name to! Is pollucite, a mineral from a is pegmatite mafic or felsic pegmatite granular and phaneritic in texture minerals. This pegmatite melt did not form in place and in equilibrium with their gabbro host have! Crystal components more trick - felsic magmas parallel to the naked eye ), mica, and beryllium tantalum–niobium! End product of the stage a magma ’ s internal differentiation process underground! Different textures depending on rate of cooling ( fast or slow ) is difficult to sample representatively due to low... Than 2.5 cm in size ( 1 in ) of 20 mm or more depending on of... Rarely are abundant a light ( felsic ) is pegmatite mafic or felsic rock and magma based on the silica content in! And sodium to your inbox to host pegmatites diorite ) are known as well a class of intrusive igneous that. Are richer in magnesium and iron a pegmatite often shows gigantic perthitic texture visible to large! A mineral from a zoned pegmatite requires login ) crystal size is the Kimberlite rock as!

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