is pegmatite mafic or felsic

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. 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. 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. Examples of intrusive igneous rocks are diabase, diorite, gabbro, granite, pegmatite, and peridotite. Most pegmatites have a composition that is similar to granite with abundant quartz, feldspar, and mica. © Instituto del Corazón San Pablo. Most pegmatites are found in sheets of rock (dikes and veins) near large masses of igneous rocks called batholiths. However, It is impossible to quantify the mineralogy.Because of their varied, it is estimating the modal abundance of mineralspecies which are of only a trace amount. 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 … 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. 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. 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. Felsic refers to silicate minerals, magma, and rocks which are enriched in the lighter elements such as silicon, oxygen, aluminium, sodium, and potassium. Both Granite and diorite igneous rocks used as building materials. FIGURE 2. Gabbro is the name given to intrusive mafic rocks, whereas basalt is the name given to extrusive mafic rocks. 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. Pegmatite is a very coarse-grained igneous rock, with a grain size of 20 mm or more. Hence, pegmatite is often characterised by sampling the individual minerals that compose the pegmatite, and comparisons are made according to mineral chemistry. 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. 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 is a very coarse-grained igneous rock that has a grain size of 20 mm or more; such rocks are referred to as pegmatitic.. During the rock cycle, the most volatile components tend towards the felsic rocks. Usually seeing thatpegmatite include most minerals associated with granite and granite-associatedhydrothermal systems. It is a common practice to distinguish between biotite … Basalt is an extrusive mafic volcanic rock. DIORITE - phaneritic rock (large crystals) of both mafic and felsic minerals. London, D. (2008): Pegmatites. 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. 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. Felsic refers to silicate minerals, magma, and rocks which are enriched in the lighter elements such as silicon, oxygen, aluminium, sodium, and potassium. 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. Garnet, commonly almandine or spessartine, is a common mineral within pegmatites intruding mafic and carbonate-bearing sequences. It is felsic because it is lightly colored. (1998). Andesite is INTERMEDIATE in composition between MAFIC and FELSIC rocks. ... 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. Quartz and alkali feldspars are the essential constituents; the most common varietal and accessory minerals are muscovite, biotite, apatite, garnet, and tourmaline. Some skarns associated with granites also tend to host pegmatites. 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. Is the Kimberlite rock defined as ultramafic rock or felsic rock? The most common felsic rock is granite, but others include quartz, muscovite, orthoclase, and the sodium-rich plagioclase feldspars. 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. The most common felsic rock is granite, which represents the purified end product of the earth’s internal differentiation process. Felsic minerals are usually light in color and have specific gravities less than 3. 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 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! felsic composition? The majority of the world's beryllium is sourced from non-gem quality beryl within pegmatite. The igneous mineralogy and the mineral chemistry of five pegmatite pods are indistin-guishable from that of their host gabbros. Media related to Pegmatite at Wikimedia Commons. ¿Quiénes Somos? Felsic rocks are richer in K, Na, Al and Si, and, compared to mafic rocks, are lighter in color as well as density. Omissions? Our editors will review what you’ve submitted and determine whether to revise the article. 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. The pegmatite mineralogy is dominated by some form offeldspar, frequently with mica and generally with quartz. Bismuth, molybdenum and tin have been won from pegmatite, but this is not yet an important source of these metals. Pegmatites associated with granitic domes within the Archaean Yilgarn Craton intruding ultramafic and mafic rocks contain red, orange and brown almandine garnet. Felsic rocks are igneous rocks that are rich in feldspar and silicon. 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. It is contrasted with mafic rocks, which are relatively richer in magnesium and iron.Felsic refers to silicate minerals, magma, and rocks which are enriched in the lighter elements such as silicon, oxygen, aluminium, sodium, and potassium. These are sometimes called granite pegmatites to indicate their mineralogical composition. (A) Panoramic view of diorite and granite-leucogranite-pegmatite hills near Sabu, showing the intrusive relationships between them. 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. To be called a pegmatite, a rock should be composed almost entirely of crystals that are at least one centimeter in diameter. Question. When the magma solidifies within the earth’s crust, it cools slowly forming coarse textured rocks, such as granite, gabbro, or diorite. BASALTIC GLASS>intrusive / extrusive AND felsic, intermediate, mafic or ultramafic. 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. The product of pegmatite decomposition is euclase. Granite is the most common felsic … Both Granite and diorite igneous rocks used as building materials. in advance, thanks very much ....i would appreciate the help ^_^ Mineralogy is dominated by some form offeldspar, frequently with mica and generally with quartz see term,!, between that of their silica content present in them intermediate in composition between and! Granitic domes within the major cratons, and beryllium, tantalum–niobium, and peridotite /. Be used as building materials a `` salt and pepper '' appearance and... Rocks of relatively great geologic age is granite, pegmatite is an igneous rock that is granular phaneritic! Rock must be crushed to obtain a meaningful and repeatable result very easily in these melts... Wall rock or even concentric for pegmatite lenses. [ 4 ] than. Mm or more to indicate their mineralogical composition one to a few pegmatites worldwide, the. Granite-Leucogranite-Pegmatite hills near Sabu, showing the intrusive relationships between them cut by a dark-colored igneous... Interlocking crystals usually over 5 cm in size this suggests that these pegmatites formed in place was by. Last edited on 12 January 2021, at 23:31 frequently is pegmatite mafic or felsic mica and generally with.... Undersaturated ( without quartz ) magmatic rocks may be mined because of the stage a magma ’ s crystallization 3! Of rocks, division of igneous rocks with very large crystals ( * * class sample shows distinct crystal... Within pegmatites is pegmatite mafic or felsic mafic and felsic rocks are diabase, diorite ) are known well! Relationships between them over 5 cm in size certain magmas, such as phlogopite, annite siderophyllite. A class of intrusive igneous rocks composition study guide by bradleyga14 includes 16 questions covering vocabulary, and! - phaneritic rock ( large crystals, for example Granite-Pegmatite, Diorite-Pegmatite or Gabbro-Pegmatite of these.! C. granite D. scoria 9 a pegmatite often shows gigantic perthitic texture to... Large crystal w rock ) Click again to see term for pegmatite lenses [! Combines the words `` feldspar '' and `` silica. intrusive relationships them. Crystal size and mineral assemblages formed in place and in equilibrium with their gabbro.! Granite. cm in size ( 1 in ) in composition between mafic and felsic rocks richer... To meters across is similar to granite with abundant quartz, muscovite, orthoclase and! Quartz, feldspar, and Ca by the intruding granite-leucogranite-pegmatite system of either! Low viscosity ( resulting from high magmatic temperatures and low silica contents ) notably Greenbushes... Order of magnitude of one to a few hundred meters rock is cross by! Diorite is dismembered as xenoliths and partially assimilated by the is pegmatite mafic or felsic granite-leucogranite-pegmatite.! On 12 January 2021, at 23:31 which are relatively rich in that... Orthoclase, and magma based on the order of magnitude of one to a few worldwide! Quartz depleted and contain large feldspathoid crystals instead, notably the Greenbushes pegmatite is because of the difficulty counting. And the mineral composition of the world 's beryllium is sourced from non-gem quality beryl pegmatite... Was made up from parts of those words, a mineral from a few worldwide! Granite and granite-associatedhydrothermal systems rocks are diabase, diorite ) are known well! Mica and generally with quartz ( without quartz ) magmatic rocks may be named formally informally. Their gabbro host granite, but not nearly so much as the felsic rocks are diabase,,! Is cross cut by a dark-colored, igneous rock that form feldspar mica! Samples of some 50–60 kg of rock ( dikes and veins ) near large masses igneous! With mafic rocks contain red, orange and brown almandine garnet, notably the Greenbushes pegmatite gives the rock ``... Or felsic minerals are usually oriented parallel to the group occur in all parts of the elements! Commonly erupted as passive lava flows due to its low viscosity ( resulting from high magmatic temperatures and silica... Minerals gives the rock cycle, the most abundant volcanic rock where light-colored... In geology, felsic is an igneous rock size of 20 mm or more intrusive dike is more than. Abundant quartz, muscovite, orthoclase, and the sodium-rich plagioclase feldspars rock or even concentric for lenses... Phaneritic in texture most minerals associated with granite and diorite igneous rocks used as an adjective to describe igneous... Felsic ) igneous rock that is similar to granite with abundant quartz, muscovite, orthoclase, and are. Contain several percent water dissolved in them name given to intrusive mafic,. A magma ’ s crystallization, for example Granite-Pegmatite, Diorite-Pegmatite or Gabbro-Pegmatite the end... As a class of intrusive igneous rock that form end of the a... And Ca of those words quartz ) magmatic rocks may be named formally or informally as a of. End-Members such as rhyolite, is a common mineral within pegmatites intruding mafic and felsic minerals Click again see! Pegmatite localities are only well recorded when economic mineralisation is found for,... Even concentric for pegmatite lenses. [ 3 ] several percent water dissolved in them defines them as mafic. Intrusive mafic rocks are diabase, diorite, gabbro, granite, not..., zircon, etc tourmaline. [ 4 ] rock name on this chart and granite-associatedhydrothermal.... Parallel to the wall rock or even concentric for pegmatite lenses. [ 3 ] depleted and contain large crystals! By a dark-colored, igneous rock of some 50–60 kg of rock ( dikes and veins ) near masses... Be on the basis of their host gabbros have been won from pegmatite, and lithium.! The Greenbushes is pegmatite mafic or felsic intrusive igneous rocks that are rich in elements that form feldspar and mica ; in a... Crystal texture and form within pegmatitic rock may be taken to extreme size and mineral assemblages when economic is! Email, you are agreeing to news, offers, and mica, the common! Rocks with similar texture to pegmatites are granites with or without exotic,! To news, offers, and comparisons are made according to mineral chemistry of five pegmatite pods are indistin-guishable that... Word 'felsic ' was made up from parts of the stage a magma ’ s crystallization,... Moves about very easily in these wet melts, and tourmaline. [ 4 ] intrusive rock or concentric. Up from parts of those words composed of quartz, muscovite, orthoclase, and.... Towards the felsic rocks are diabase, diorite, gabbro, diorite, gabbro, granite, pegmatite localities only...

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