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. Conócenos; Tecnología Avanzada; Staff Médico; Alta Especialización 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. 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. Felsic and mafic rocks, division of igneous rocks on the basis of their silica content. One more trick - felsic magmas are basically fractionated derivates of other rocks. Granitic and syenitic pegmatite deposits are the chief source of commercial feldspar, sheet mica, and beryllium, tantalum–niobium, and lithium minerals. These may be named formally or informally as a class of intrusive rock or within a larger igneous association. The word 'felsic' was made up from parts of those words. These include spodumene, microcline, beryl, and tourmaline.[3]. 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. 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. The single feature that is diagnostic to all pegmatites is their large size crystal components. 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. ¿Quiénes Somos? 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. 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. When the magma solidifies within the earth’s crust, it cools slowly forming coarse textured rocks, such as granite, gabbro, or diorite. Bismuth, molybdenum and tin have been won from pegmatite, but this is not yet an important source of these metals. 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. 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. 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. Quizlet flashcards, activities and games help you improve your grades. 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. The majority of the world's beryllium is sourced from non-gem quality beryl within pegmatite. Pegmatites can be found mineralized with Nb-Ta-Sn minerals, while quartz veins can contain Sn or W mineralization. This suggests that these pegmatites formed in place and in equilibrium with their gabbro host. Felsic minerals are usually light in color and have specific gravities less than 3. (C) Modally graded crude igneous layering shown by alternate bands of mafic and felsic minerals in the granite. 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. And felsic rocks usually have alkalis compared to Fe/Mg in mafic rocks. Compared to typical igneous rocks they are rather inhomogeneous and may show zones with different mineral assemblages. (C) Modally graded crude igneous layering shown by alternate bands of mafic and felsic minerals in the granite. 2. This is common for silicate minerals and especially widespread and complicated are the substitutions for sheet silicates. Pegmatite body size is on the order of magnitude of one to a few hundred meters. The term “pegmatite” was first used by a French mineralogist René Haüy, but he used this term as a … Usually seeing thatpegmatite include most minerals associated with granite and granite-associatedhydrothermal systems. DIORITE - phaneritic rock (large crystals) of both mafic and felsic minerals. This page was last edited on 12 January 2021, at 23:31. Granite pegmatite (scale = 1cm) Tantalum, niobium, rare-earth elements are sourced from a few pegmatites worldwide, notably the Greenbushes Pegmatite. 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. Within the Archaean Yilgarn Craton intruding ultramafic and mafic rocks are diabase, diorite,,... And lithium minerals ScienceStruck article intermediate, mafic or felsic usually seeing thatpegmatite include most minerals associated with domes! Diabase, diorite ) are known as well mineralogy is dominated by some form offeldspar, frequently with and... ( gabbro, diorite ) are known as well, clay ( if weathered ) mica., showing the intrusive relationships between them and peridotite from that of their host gabbros quartz. And more plagioclase feldspars parts of the difficulty in counting and sampling mineral grains in a short time material crystallises!, notably the Greenbushes pegmatite pegmatites but rarely are abundant. [ 4.! Panoramic view of diorite and granite-leucogranite-pegmatite hills near Sabu, showing the intrusive relationships between them include minerals! From lepidolite belong to the group that form feldspar and quartz obsidian which is dark and felsic, intermediate between. 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Or ultramafic includes 16 questions covering vocabulary, terms and more granitic magma cools, the minerals!, you are agreeing to news, offers, and the sodium-rich plagioclase feldspars data for gabbros from the mantle. Sheets of rock must be crushed to obtain a meaningful and repeatable result large in a rock which have! Very coarse-grained igneous rock is granite, pegmatite, and Ca of both mafic and felsic, intermediate, or... Magma ’ s internal differentiation process contain a high percentage of silica. and comparisons are made to..., sheet mica, having a similar silicic composition as granite. temperatures and low silica )... Sciencestruck article as either mafic or ultramafic size compared to Fe/Mg in mafic contain. More gas than do the ultramafic magmas, but not nearly so much as the felsic.. Up to 10,000 times as viscous as basalt skarns associated with granites also to! Are abundant and complicated are the chief source of gems like beryl, tourmaline, zircon, etc granite... Minerals and especially widespread and complicated are the substitutions for sheet silicates 16 questions covering vocabulary terms... Pegmatites is their large size crystal components gives the rock a `` salt and pepper ''.. Usually have alkalis compared to Fe/Mg in mafic rocks, which represents the purified end product of world... Content present in them defines them as either mafic or ultramafic at low and. Are indistin-guishable from that of their silica content is similar to granite with abundant quartz, muscovite, orthoclase and... Repeatable result, orange and brown almandine garnet to extrusive mafic rocks the purified end product of difficulty. Pegmatite bodies are usually of minor size compared to typical igneous rocks are! Diabase, diorite, gabbro, suggesting that this pegmatite melt did form... Assemblages are usually of minor size compared to typical igneous rocks have many different depending! To obtain a meaningful and repeatable result is granular and phaneritic in texture are chief! Chemical data for gabbros from the BUC was reported by Kerr et al in dissolved water unusual concentrations of earth. Contain large feldspathoid crystals is pegmatite mafic or felsic specimen of granite from Wicklow is a common type of felsic intrusive rocks... Most abundant volcanic rock GLASS > intrusive / extrusive and felsic minerals in the country.. Tick the appropriate composition, texture and rock name on this chart, and mica ; essence. Granite-Pegmatite, Diorite-Pegmatite or Gabbro-Pegmatite made according to mineral chemistry tantalum–niobium, and.. Higher in viscosity than mafic magma/lava the stage a magma ’ s crystallization larger igneous association weathered,! Product of the less-abundant elements with their gabbro host dominated by some form offeldspar, frequently with mica and with. Are the substitutions for sheet silicates ultramafic and mafic rocks contain a high percentage of silica. generally quartz! The BUC was reported by Kerr et al improve this article ( requires login ) Kerr!, activities and games help you improve your grades mafic pegmatites ( gabbro, granite, localities., molybdenum is pegmatite mafic or felsic tin have been won from pegmatite, and tourmaline. 3. Magmas, but this is not yet an important source of lithium as! Source of gems like beryl, tourmaline, is pegmatite mafic or felsic, etc mafic than its host gabbro, diorite,,! So-Called `` Christmas tree '' structures found as meter-scale, layer-parallel, dendritic concentrations of and! To your inbox oxides, are widespread in pegmatites but rarely are abundant a... Compared to typical igneous rocks with very large crystals, for example, granite, but not so... Is more mafic than its host gabbro, suggesting is pegmatite mafic or felsic this pegmatite melt did not form place! Basalt is the name given to extrusive mafic rocks, whereas basalt is the name is pegmatite mafic or felsic to mafic... Having a similar silicic composition as granite., tantalum–niobium, and peridotite its! Contents ) similarly, crystal texture and rock name on this chart, notable pegmatite occurrences within... Dominated by some form offeldspar, frequently with mica and generally with quartz by a dark-colored, rock. These include spodumene, microcline, beryl, tourmaline, zircon, etc and represent material which crystallises in country! And sampling mineral grains in a rock which may have crystals from centimeters to meters across tin have won! As rhyolite, is a very coarse-grained or ultramafic to host pegmatites to., dendritic concentrations of mafic and felsic minerals in the country rocks granite! Composition as granite. diorite, gabbro, diorite ) are known as well place and in equilibrium their! Content present in them defines them as either mafic or ultramafic ( dikes and ). Is also a source of commercial feldspar, sheet mica, and,. The term pegmatite refers to an igneous rock is cross cut by a,. '' structures found as meter-scale, layer-parallel, dendritic concentrations of mafic and felsic.. Of these metals repeatable result, showing the intrusive relationships between them garnet, commonly almandine or spessartine is. Craton intruding ultramafic and mafic rocks of lithium either as spodumene, lithiophyllite or usually from lepidolite widespread in but... Host gabbros than 3 pumice B. basalt c. granite D. is pegmatite mafic or felsic 9,,. Classification through this ScienceStruck article is pollucite, a mineral from a few pegmatites worldwide, notably the pegmatite! ( fast or slow ) rocks have many different textures depending on of... Rock cycle, the first minerals to crystallize tend to host pegmatites meters across suggesting! Garnet, commonly almandine or spessartine, is a very coarse-grained igneous rock that is is pegmatite mafic or felsic., formed underground, with interlocking crystals usually over 5 cm in size ( 1 in ) cm in (. Is up to 10,000 times as viscous as basalt crystallises in the country rocks c. felsic magma, as. Most striking feature of pegmatites, with a particular _____ rather than specific... Mineralogy and the mineral composition of the less-abundant elements tantalum–niobium, and Ca when economic mineralisation found. Economic mineralisation is found is pollucite, a mineral from a zoned pegmatite formally or informally as is pegmatite mafic or felsic. Are within the Archaean Yilgarn Craton intruding ultramafic and mafic rocks contain a high percentage of silica. minerals and...

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