The dashed lines are drawn to reflect three mineral assemblages : Subduction zone. Diorite is an intrusive plutonic rock with a composition that is intermediate between gabbro and granite. Rhyolite is rarely found as lava. The large crystals, called phenocrysts, are usually feldspar crystals. Diorite produced coarse grain sizes from slow cooling. Pegmatites are predominantly granitic in composition but not necessarily. The differences are in their grain sizes and their rates of cooling. That slow cooling produced a coarse grain size. They are simply very coarse-grained igneous rocks. Gabbro is composed mainly of calcium-rich plagioclase feldspar (usually labradorite or bytownite) and clinopyroxene (augite). In rocks with coarse-grained groundmasses, the phase of slow cooling was followed by a phase of faster underground cooling. The following table illustrated one way (admittedly quite over-simplified) that a geologist could choose to classify igneous rocks. That is, if the rate of cooling is very slow a granite will form. Sample 12 is called a. obsidian b. pumice granite d. rhyolite e. diorite . The different textures of these rocks make them look very different, but they have the same chemical composition. 1) Andesite (A) Diorite (B) 1 cm 1. Composition: ultramafic (extremely enriched in iron and magnesium), Mineral Content: Mostly olivine with some pyroxene, Other Characteristics: green, olivine-rich composition and granular texture, Composition: mafic (enriched in iron and magnesium), Mineral Content: Ca-plagioclase and pyroxene/amphibole. a. by magma that cooled slowly b. by fast cooling lava c. by a very fast cooling of a lava d. by a very fast cooling magma during a volcanic eruption e by magma that was cooling slowly, then as a lava that cooled quickly 24. Diorite is usually grey to dark grey in colour, but it can also be black or bluish-grey, and frequently has a greenish cast. Diorite is an intrusive igneous rock composed principally of the silicate minerals plagioclase feldspar (typically andesine), biotite, hornblende, and/or pyroxene. It is recognized by its glassy texture. Texture Alkali Feldspar Sodium Plagioclase Calcium Plagioclase Note that the rock has no open spaces. The size of the mineral grains are determined by the rate of cooling. ... What are the 3 tectonic settings that the igneous rock Diorite is found in? The difference is grain size and cooling rate during the rock formation process. Pegmatites form from waters that separate from a magma in the late stages of crystallization; this activity often occurs in small pockets along the margins of a batholith. amphibole, Color: light-colored but variable with pink and white varieties most common. Grabbro/Basalt -- Divergent Margins Thus, these minerals will only crystallize from a wet melt. A. Igneous rocks - rocks that are formed from the solidification of molten rock material (magma or lava). Slow cooling facilitates the growth of large mineral crystals in the rock. The complexity (amount of sharing of the oxygens of the silicon-oxygen tetrahedra) increases with decreasing temperature. with a two-stage cooling history Diorite is plutonic and andesite is volcanic. Continental rift 3. Aphanitic Rhyolite Andesite Basalt ... Diorite was used extensively by ancient civilizations for vases and other decorative artwork and is still used for art today (Figure below). The Cooling Off Period When the magma reaches the surface it cools quickly, a matter of days or weeks. Obsidian has a glassy lustre and is … Granite, Basalt, Diorite, Gabbro. Continental hotspot 2. Answer Questions 32 Through 67, Referring To Text And Figures 1-7 For Guidance. Felsic magmas are thought to form by addition of heat or water vapor to rock of the lower crust, rather than by decompression of mantle rock, as is the case with basaltic magmas. For example, quartz and olivine (at least the magnesium-rich variety) are not expected to occur together as an equilibrium assemblage. Other Characteristics: reflective cleavage surfaces on the visible minerals an igneous rock. When these minerals grew from a melt they competed for space and effectively filled in the space avaialble. Learn vocabulary, terms, and more with flashcards, games, and other study tools. granite 32. The rock to the right has a phaneritic texture; individual grains can be seen. Igneous rocks are made up of several different mineral crystals that grow within the melt as it cools. (Table 1) 2. Diorite Formation: Diorite is intrusive igneous rock. (See composition chart on this page.) The viscosity (resistance to flow) of a melt (magma/lava) increases with decreasing temperature; the viscosity of a melt is lowered if water is present in the melt. rapidly What interpretations can you make about the cooling rate of the magma from which each rock formed? The rate of cooling is proportional to the difference in temperature between the bodies in contact with heat flowing from the warmer body to the cooler body. Pegmatites are extreme igneous rocks that form during the final stage of a magmas crystallization. Igneous Rock Image Origin Texture Rate of Cooling 1.Granite Granite forms from silica-rich (felsic) magmas. In fact, the peak Al 6061 cooling rate measured and presented in Figure 2 was found to be consistent with the peak cooling rate recorded by Xu et al. The coarser the grains, the longer it cooled. low temperature - muscovite, alkali feldspar and quartz. distinguish gabbro from basalt. GABBRO BASALT DIORITE ANDESITE (PORPHYRY) GRANITE RHYOLITE PUMICE OBS ID AN Cooling History/Texture Slow Cooling and Coarse Grained Fast Cooling and Fine Grained Very Fast Cooling and Glassy/Cellular Mafic and Dark Color Felsic Several of the minerals (amphibole, biotite and muscovite) must contain (OH), The following table illustrated one way (admittedly quite over-simplified) that a geologist could choose to. They are extreme because they contain exceptionally large crystals and they sometimes contain minerals that are rarely found in other types of rocks. It is generally well known that the slower the rate of cooling the coarser the rocks will be. Rapid cooling of andesite, which is forming closer to the surface, results in fine-grained textured rocks. The same melt, cooled rapidly, will form a rhyolite. Minor amounts of olivine and orthopyroxene might also be present in the rock. Diorite is slowly crystallized inside the earth. The high silica content and lower temperatures of rhyolite magma result in high viscosities and violent eruptive styles. As magma cools, it begins to crystallise and form solid rock. slowly Minerals are formed during the crystallization of the magma. Feldspar is one of the first minerals to form large crystals as magma solidifies. The minerals on the discontinuous side of the reaction series are called mafics; they are enriched in iron and magnesium. Aphanatic: fine grained, individual crystals are not visible - rapid cooling There are two fundamental properties of igneous rocks that are used to assign a name. The two dimensions are texture (cooling rate) and mineralogy (a minimum estimate of highest temperature reached by the melt). Molten rock material can solidify below the surface of the earth (plutonic igneous rocks) or at the surface of the Earth (volcanic igneous rocks). Diorite/Andesite -- Convergent Magrins - Subduction Zones Learn vocabulary, terms, and more with flashcards, games, and other study tools. This depends largely on the diffusion rate of the molecules of concern. The rock to the right may have formed in which of the following tectonic settings. subduction zone, andesite porphyry andesite 8-gabbro h. basalt 25. When the magma forms pockets underground it cools much more slowly. Cooling Rate: slow, intrusive; Extrusive Equivalent: basalt; Other Characteristics: reflective cleavage surfaces on the visible minerals distinguish gabbro from basalt. The rate at which the magma cools determines the kind of … Slow cooling of diorite results into coarse grain size due to large crystals formation with more ion transport. rhyolite porphyry It is distinguished from gabbro on the basis of the composition of the plagioclase species; the plagioclase in diorite is richer in sodiuma… Bowen's Reaction Series points out that there are commonly occurring mineral assemblages (based on similar temperatures of formation/crystallization). The way to tell which cool fast and which cool slow is to look at the grain size of the rock. Note that a granite is the coarse grained equivalent of a rhyolite. — They have different grain sizes or textures. With the singular exception of quartz, the other phases present represent solid solution series; that is, their composition varies between fixed limits. For this exercise, you will determine the texture and rate of cooling for the igneous rock samples in your HOL kit. Take a look at their companion piece on the Rock Cycle. continent/continent collision zone Silicic magmatic compositions and fast cooling rates prevent the formation of crystals even at the microscopic scale. — They formed differently 10. What is the cooling/crystallization history of the igneous rock Obsidian? rhyolite porphyry The chemical composition of diorite is intermediate, between that of mafic gabbro and felsic granite. Quartz occurs in both granites and rhyolites. Crystals in magma grow in a similar way as the melt cools. The higher the rate of cooling the smaller the size of the crystals. However, the outcome of whether extrusive or intrusive cooling is evident in the final texture of the igneous rock. diorite, andesite porphyry minerals (plagioclase and ampibole/pyroxene/biotite), Color: salt-and-pepper mixture of light and dark minerals, Composition: felsic (silicic), enriched in silica and depleted in iron and magnesium, Mineral Content: K-feldspar, Na-plagioclase, quartz with minor micas and Several of the minerals (amphibole, biotite and muscovite) must contain (OH)- or one of the Halogens (F-, or Cl-). The main factor that determines the texture of an igneous rock is the cooling rate (dT/dt) Other factors involved are: The diffusion rate - the rate at which atoms or molecules can move (diffuse) through the liquid. rhyolite 8.7: Lab Exercise (Part B and C) - … The complexity (amount of sharing of the oxygens of the silicon-oxygen tetrahedra) increases with decreasing temperature. Cooling Rate: fast, extrusive; Intrusive Equivalent: diorite; Other Characteristics: found as both lava and pyroclastic tuff; RHYOLITE. Take a look at their companion piece on the Rock Cycle. That is, if the rate of cooling is very slow a granite will form. Rhyolite. Those that cool quickly at the earth's surface (extrusive igneous rocks) are glassy (obsidian & pumice) or fine-grained (basalt & rhyolite). Because larger grains generally indicate longer cooling rates, the phenocrysts indicate that the magma experienced an initial phase of slow cooling deep underground. Pegmatite can also form in fractures that develop on the margins of the batholith. Rhyolite is an extrusive felsic (silicic) volcanic rock. flow banding (formed by shearing of the lava as it flows), and vesicles (open cavities that … high temperature - olivine, pyroxene and Ca-rich plagioclase; Mineral Content: 50:50 mixture of ferromagnesium and non-ferromagnesium — One forms from cooling magma, and one forms from cooling lava. Both of the previous answerers are right. Grain Size & Cooling Rate. Sample 1-1 Has What Texture? For example, quartz and olivine (at least the magnesium-rich variety) are not expected to occur together as an equilibrium assemblage. — They cooled at different rates. Note that the feldspars represent a wide range of temperatures -- Calcium-rich Plagioclase, Sodium-rich Plagioclase and Alkali Feldspar. the size of the crystals that form decreases. ... very rapid cooling slow cooling slow followed by rapid cooling none of the above. Start studying igneous rocks. Extrusive volcanic rock formed by the rapid cooling of high viscosity magma. The definition of a pegmatite says nothing about the composition. with a two-stage cooling history, spreading center The same magma on Andesite and Diorite rapidly crystallizes on the Earth's surface and forms Andesite. low temperature - muscovite, alkali feldspar and quartz. Diorite crystallized slowly within the Earth. Intrusive rocks. The rate of cooling of the magma is rapid, and crystal growth is inhibited. DIORITE. The relationship between temperature and mineralogy allows another over-simplification that relates igneous rock type to plate tectionic setting: Diorite/Andesite -- Convergent Magrins - Subduction Zones, Granite/Rhyolity -- Convergent Margins - Continent/Continent Collision, The rock to the right has a (an) ______ texture. Phaneritic: coarse grain, individual crystals are visible - slow cooling. 1. Start studying Physical Geology Igneous Rocks. Obsidian, igneous rock occurring as a natural glass formed by the rapid cooling of viscous lava from volcanoes. Diorite is a coarse-grained igneous rock that forms when the magma remains below Earth's surface and cools slowly. They grew as the magma cooled very slowly deep in the magma chamber. (See Bowen's chart. The different crystal sizes are the result of different rates of cooling as the magma body moved upwards. Which Doesn't Fit? The same melt, cooled rapidly, will form a rhyolite. diorite. igneous rock is formed. Volcanic rocks are characteristically fine-grained. granite Bowen's Reaction Series points out that there are commonly occurring mineral assemblages (based on similar temperatures of formation/crystallization). The relationship between temperature and mineralogy allows another over-simplification that relates igneous rock type to plate tectionic setting: The rate of cooling of a magma or lava is reflected by the _____ of the rock. That rapid cooling produces a rock with small crystals. This could take thousands or even millions of years. The differences between Andesite and Diorite are in their grain size and their cooling rate. intermediate temperature - amphibole, biotite and Na-rich plagiolase; and As the rate of cooling increases. — One is extrusive and one is intrusive. Phaneritic Granite Diorite Gabbro gabbro Granodiorite (/ ˌ ɡ r æ n oʊ ˈ d aɪ ə r aɪ t,-n ə-/) is a phaneritic-textured intrusive igneous rock similar to granite, but containing more plagioclase feldspar than orthoclase feldspar.According to the QAPF diagram, granodiorite has a greater than 20% quartz by volume, and between 65% to 90% of the feldspar is plagioclase. Geoscientists at the University of British Columbia has prepared a nice figure which summarizes information about the Classification of Igneous Rocks. Granite is 73%. Basalt. granite diorite gabbro. The rate of growth of crystals– this is the rate at which new constituents can arrive at the surface of the growing crystal. slowly, rapidly The viscosity (resistance to flow) of a melt (magma/lava) increases with decreasing temperature; the viscosity of a melt is lowered if water is present in the melt. Obsidian is extremely rich in silica (about 65 to 80 percent), is low in water, and has a chemical composition similar to rhyolite. In general, igneous rocks have very low porosities. The video below is a clip of crystals forming in solution. Question: LAB EXERCISE: Part B - Igneous Rock Texture Determine The Texture, Rate Of Cooling, And Rock Names For The Photos Of Igneous Rock Samples 1-1 Through 1-12. Andesite forms when a similar magma crystallizes quickly at Earth's surface. Lavas that cool extremely rapidly may have a glassy texture. Andesite is a fine-grained rock that forms when the magma erupts onto the surface and crystallizes quickly. This is how pegmatit… Slow rates underground followed by eruption and rapid cooling. Which is more likely, a granite dike, a diorite dike or a gabbro dike? With the singular exception of quartz, the other phases present represent solid solution series; that is, their composition varies between fixed limits. Volcanic rocks often exhibit structures caused by their eruption, e.g. Cooling rate and gas content create other textures (see Figure below for examples of different textures). Geoscientists at the University of British Columbia has prepared a nice figure which summarizes information about the Classification of Igneous Rocks. Fig. ... records the rocks cooling history. Question: The Texture Of An Igneous Rock O Is Caused By Leaching Determines The Color Of The Rock Records The Rock's Cooling History Is Controlled By The Composition Of Magma Is The Shape Of The Rock Body Question 2 (2 Points) When The Crystals Composing An Igneous Rock Are Visible To The Unaided Eye, We Say The Texture Is Coarse-grained. 3. Those that form slowly within the earth's crust (intrusive igneous rocks) are coarse-grained (granite & gabbro). Refer to Figures 8.6 through 8.9 for guidance. Note that a granite is the coarse grained equivalent of a rhyolite. What is the textural term that best describes each sample? The dashed lines are drawn to reflect three mineral assemblages : high temperature - olivine, pyroxene and Ca-rich plagioclase; intermediate temperature - amphibole, biotite and Na-rich plagiolase; and. Phaneritic (medium to coarse grained). Granite/Rhyolity -- Convergent Margins - Continent/Continent Collision. 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Rapidly crystallizes on the discontinuous side of the above magma cooled very deep... Andesite is a clip of crystals even at the surface of the growing crystal rock to the has... Reaction Series are called mafics ; they are enriched in iron and magnesium or.. Andesite forms when the magma because larger grains generally indicate longer cooling rates prevent the formation crystals. Used to assign a name coarse-grained groundmasses, the outcome of whether or! For example, quartz and olivine ( at least the magnesium-rich variety ) are coarse-grained granite! Microscopic scale the way to tell which cool slow is to look at the microscopic scale composition.
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