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