Metamorphic differentiation rocks are inhomogeneous so is the deformation in rocks experiencing shear separation of high and low shear zones by transition zones. The chart below summarizes the parent rock, setting, and grade of common metamorphic rocks. Grade of metamorphism metamorphic grade is a general term for describing the relative temperature and pressure conditions under which metamorphic rocks form. This parallel alignment causes the rock to split easily into thin layers or sheets. Foliation is common in aphanitic as well as phaneritic metamorphic rocks. Jan 04, 2016 classification of metamorphic rocks based on texturestructures phyllite similar to slate, but slightly coarser phyllosilicate grains grains can be seen in hand specimen, giving silk appearance to cleavage surfaces often cleavage planes less perfectly planar than slates slate strongly cleaved rock cleavage planes are developed due to. Lightcolored dikes and sills of igneous rock cut the metamorphic rocks. Textures of metamorphic rocks excess energy present in deformed crystals elastic, twins, surface free energy growth of new grains leads to decreasing free energy release elastic energy, reduce surface to volume ratio increase grains size, exception occurs in zones of intense shearing where a number of nuclei are formed. During metamorphism the protolith undergoes changes in texture of the rock and the mineral make. Sedimentary rocks are formed from the cementing together of sediments, or from the compaction squeezing together of sediments, or from the recrystallization of new mineral grains which are larger than the original. Callegari, department of science, mineralogy and petrology, university of torino, italy. Gneiss is an example and is found in karnataka, andhra pradesh, tamil nadu, madhya pradesh, orissa and some parts of jharkhand and rajasthan. Many precious materials, such as marble and many types of gemstones, including diamonds, are formed by the metamorphic process. With increasing pressures and temperatures, phyllite.
How are metamorphic rocks different from igneous and sedimentary rocks. Foliated metamorphic rocks are generally associated with regional metamorphism. Phyllosilicates accommodate better shear other minerals dissolve due to high shear. All chapters of part ii of the book have been rewritten. They have a significant amount of sheet silicate platy minerals and are classified by composition, grain size, and. Read this sciencestruck article to gain extensive information about the main. As per wikipedia, metamorphic rocks arise from the transformation of existing rock types, in a process called metamorphism, which means change in form. Metamorphic rocks pictures of foliated and nonfoliated types. Petrogenesis of metamorphic rocks raregeologybookss blog. Metamorphic rock has been transformed, while in the solid state, by pressure, temperature and deformation. Apr 20, 2017 metamorphic differentiation rocks are inhomogeneous so is the deformation in rocks experiencing shear separation of high and low shear zones by transition zones. Metamorphic rocks are formed when other types of rocks change because of the enormous pressure and heat they experience deep within the earth. The domain of this classification system includes not only metamorphic rocks as commonly understood, but also a variety of hydrothermally altered, myloniteseries, cataclastic, and impactmetamorphic rocks. Rocks are formed on earth as igneous, sedimentary, or metamorphic rocks.
Metamorphic rocks were once igneous or sedimentary rocks, but have been changed metamorphosed as a result of intense heat andor pressure within the. These can range from textures similar to the original protolith at low grades of metamorphism, to textures that are purely produced during metamorphism and leave the rock with little resemblance to the original protolith. They are formed by both increasing pressures and temperatures. Metamorphic rock is one of the 3 major classes of rock comprising the earths crust, the others being sedimentary and igneous rocks. Metamorphic rock types there are two major subdivisions of metamorphic rocks. Also, the chapters introduction and grade have undergone several major changes. Discuss the mode of occurrence and characteristic textures common in metamorphic rocks. Igneous rocks form when rocks are heated to the melting point which forms magma.
Figure 3 classification scheme for metamorphic rocks. Below is an alphabetical list of metamorphic rocks. Learn vocabulary, terms, and more with flashcards, games, and other study tools. Classification of metamorphic rocks based on texturestructures phyllite similar to slate, but slightly coarser phyllosilicate grains grains can be seen in hand specimen, giving silk appearance to cleavage surfaces often cleavage planes less perfectly planar than slates slate strongly cleaved rock cleavage planes are developed due to.
Metamorphic rocks have been modified by heat, pressure, and chemical processes, usually while buried deep below earths surface. We can measure the mineral compositions and assemblage i. Metamorphic rocks are former igneous, sedimentary or metamorphic rocks that have changed their texture and composition. Types of rocks igneous sedimentary rocks metamorphic. The mineral constituents of foliated metamorphic rocks are oriented in a parallel or suhparallel arrangement.
Metamorphism is the addition of heat andor pressure to existing rocks, which causes them to change physically andor chemically so that they become a new rock. In common usage, schists are restricted to those metamorphic rocks in which the foliated minerals are coarse enough to see easily in hand specimen. Names that are not linked are ones for which picturesdescriptions are not yet available. We classify these compositegenesis rocks according to descriptive properties that reflect the multiple processes that make the rock composite. At that time neptunists and plutonists were still debating the sedimentary vs igneous origin of granitic rocks, and the terms. Its the first thing you learn in a geology class very briefly the three types of rocks are igneous they form from the cooling of magma deep inside the earth. Types of metamorphic rock collecting rocks and minerals. If you know the name of a rock and want to learn more about it, clicking on the name will take you to a picture and a description. Metamorphism and metamorphic rocks chapter questions. Callegari, department of science, mineralogy and petrology, university of torino, italy 2 n. Dynamic metamorphics are the rocks that have been experiencing dynamic pressure.
Another set of metamorphic rock names, which are commonly formed by combining mineral names with structural terms for example, quartzmica schist. Normally, the two types of layers have the same kinds of minerals, but in different proportions, giving. Following are the classification of rocks in india. Parent rocks the rock that the metamorphic rock comes from. If the temperature of metamorphism is high enough for partial melting of the rock to occur, the changes would still be called metamorphism until the melt is.
Metamorphic settings b, r, s b, r, s s b, r, s b, r, s parent rock shale granite basalt chert sio2 limestone. The rocks provide clues to their transformation into a metamorphic rocks. This type of metamorphic was created by regional metamorphism, in which a sedimentary or igneous rock has been deeply buried and subjected to high temperatures and pressures. The domain of this classification system includes not only metamorphic rocks as commonly understood, but also a variety of hydrothermally altered, myloniteseries, cataclastic, and impact metamorphic rocks. If a rock is foliated, its name is determined by the type of foliation present and the dominant mineralsfor example, a kyanite schist. The rocks within a mountain chain not only sustain considerable pressures but are also heated both generally and by the large scale of intrusion of magma, with the effect that rocks are deformed and recrystallized to varying degrees. A metamorphic rock is an igneous, sedimentary, or another metamorphic rock that has either been squeezed by incredible pressures deep underground andor has been exposed to very high temperatures, altering its structure, mineral alignment, or chemical composition. Metamorphic grade is the extent or rank of metamorphism, measured by the amount of degree of difference between the parent rock and the metamorphic rock according to the agi glossary of geology. How to name a metamorphic rock british geological survey. Agents of metamorphism heat pressure chemical activity heat is the most important agent of metamorphism. Examples of foliated rocks are slate, shale, and gneiss. Origin, texture, and classification of metamorphic rocks. Note that classification is generally loose and practical such that names can be adapted to describe the rock in the most satisfactory way that conveys the important characteristics. Because of how they are formed, metamorphic rocks constitute a great deal of the bedrock in earths crust.
Metamorphic rocks are classified by texture and by mineral composition. Changes occur in the solid state because melting doesn t occur. Metamorphic rocks are best identified when looking at the rock as you see them in nature. Normally a geothermal gradient increases in temperature with depth at about 30c per kilometer. The three main types, or classes, of rock are sedimentary, metamorphic, and igneous and the differences among them have to do with how they are formed. Metamorphic rocks form when rocks are subjected to high heat, high pressure, hot mineralrich fluids or, more commonly, some combination of these factors. The bands in foliated metamorphic rock look like pages in a book. Mathscience nucleus 2001 1 metamorphic rocks teacher guide including lesson plans, student readers, and more information lesson 1 formation of metamorphic rocks lesson 2 metamorphic rock classification chart lesson 3 metamorphic rocks lab lesson 4 the many facies of metamorphic rocks lesson 5 michelangelo and marble designed to be used as an. Metamorphic rocks started out as some other type of rock, but have been substantially changed from their original igneous, sedimentary, or earlier metamorphic form.
Special case metamorphic rock groups and their place. Metamorphic textures and mineralogy develop progressively over several hundreds of feetmeters of drilling. Explain what an open and closed metamorphic system is. They are formed when sedimentary and igneous rocks become changed by pressure and heat. The process requires millions of years in transformation. Exposure to these extreme conditions has altered the mineralogy, texture, and chemical composition of the rocks.
Note the strong vertical fabric of the canyon wall. Experiments suggest that the time involved is tens of millions of years. Metamorphism and metamorphic rocks tulane university. The preexisting rocks may be igneous, sedimentary, or other metamorphic rocks. Generally, metamorphic grade is closely associated with the maximum temperature of metamorphism so that highergrade rocks have experienced higher. Because they start as other rocks, there are many types. In the large outcrop of metamorphic rocks in figure 1, the rocks platy appearance is a result of the process metamorphism. Concise information about metamorphic processes, with excellent cartoon of mineral growth during compression. Nearly all traces of the original structures including fossils and fabric such as layering and ripple marks are wiped out as the minerals migrate and recrystallize. For example, slate and marble are building materials, garnets are used as gemstones. The process by which metamorphic rocks are produced is called metamorphism. By this definition schist is a broad term, and slates and phyllites are also types of schists. This new edition of petrogenesis of metamorphic rocks has several completely revised chapters and all chapters have updated references and redrawn.
Keep reading to know more metamorphism is a geological process involving rocks changing their form. Read this sciencestruck article to gain extensive information about the main features of these rocks. Metamorphism metamorphic environment is classified as regional, contact, dynamic, burial, hydrothermal, impact, metamorphism along fault zones. Characteristics of metamorphic rocks science struck. Change is a result of pressure directed stress and heat solid state reaction no net change in chemistry ideally role of groundwater recrystallization of new minerals from old minerals. Metamorphic rock metamorphic rocks are formed when preexisting rocks are exposed to extreme heat and pressure metamorphic rocks are found deep within earths crust, so there is a lot of rock on top pressing down. A process of change 1 metamorphic rock forms from a preexisting rock or protolith. As a metamorphic rock it is considered of low grade and it can be split into thin pieces very easily. Rocks that become metamorphic are so deep in the crust that they are very close to the mantle. As the rock crystallizes or recrystallizes under directed pressure, new crystals may grow in some preferred. Classification of metamorphic rocks depends on what is visible in the rock and its degree of metamorphism. They have been stretched or flattened, maybe twisted when large scale movements happen in the earths crust and different rock masses are forced over each other and crush each other as they come into contact.
Deep underground rocks are exposed to high pressures from the overlying layers of rocks and high temperatures from magma. Field description of metamorphic rocks the basic procedural aspects of writing a description for metamorphic rocks or rock units are identical to those for sedimentary rocks and rock units. Lecture notes metamorphism introduction metamorphism is a change of form that includes the growth of new minerals, typically in response to a rise in temperature and normally without the involvement of a magma. Metamorphic comes from the greek word meta and morph, meaning change in form. Gallery of photographs of highgrade metamorphic rocks. Foliated metamorphic rocks foliated metamorphic rocks are those in which the minerals have been flattened and pushed down into parallel layers. Metamorphic rock, any rock that results from the alteration of preexisting rocks in response to changing conditions, such as variations in temperature, pressure, and mechanical stress, and the addition or subtraction of chemical components. These rocks include slate, phyllite, schist, gneiss, granulate and migmatite. Banding means that the rock consists of alternating, thin layers typically 1 mm to 1 cm of two different mineral compositions. Regionals are the rocks that have the schisty texture which break along the layers except gneiss. As the rock crystallizes or recrystallizes under directed pressure, new crystals may grow in some preferred direction, sometimes.
Contact metamorphic rocks british geological survey. Outline the role of volatiles in metamorphic processes. Igneous and sedimentary rocks eroded by wind, weather and water become metamorphic rocks. Classification classification of metamorphic rocks depends on what is visible in the rock and its degree of metamorphism. Sedimentary rocks are formed from the cementing together of sediments, or from the compaction squeezing together of sediments, or from the recrystallization of new mineral grains which are larger than the original crystals. Metamorphic rocks in nature shale to slate metamorphism deformation of sedimentary rocks metamorphic rocks record how temperature and pressure affected an area when it was forming. The simplest planar features may be primary bedding akin to the layering in sedimentary rocks. Metamorphic rocks are usually highly deformed because they have been subjected to high temperature and pressure. Metamorphic rock textures chemeketa community college. Summarize the progression of different rock types produced by regional. At low pressures and temperatures, the sedimentary rock shale forms slate. Without careful examination by the geologist, and the recognition of the subtle changes in mineralogy and texture, much time and money can be wasted by drilling past the economic basement. Geology of the north cascades scenic metamorphic rocks.
Foliated these have a planar foliation caused by the preferred orientation alignment of minerals and formed under differential stress. Their study provides us with important data regarding formation of the earth and the past geological environment. Stages of metamorphism foliated rocks slate schist gneiss gneiss stripes. Ii origin, texture, and classification of metamorphic rocks teklewold ayalew encyclopedia of life support systems eolss some metamorphic rocks, particularly those buried to depths of several kilometers, contain numerous veins rich in quartz and feldspar. Main types of metamorphism regional metamorphism is a type of metamorphism which occu rs over an area of wide extent, that is, affecting a large rock vo lume, and is associated with largescale tectonic processes, such. Metamorphic rock names based on parent rock, geologic setting, and metamorphic grade. These rocks get this name as they are formed from the hot molten earth and are the oldest and primary rocks. As for the last of these three foliating types of metamorphic rocks, schist is also a rock that can be broken into thinner pieces due to the great amount of mika contained in it and its well developed foliation. The most obvious features of metamorphic rocks are certain planar features that are often termed ssurfaces. Metamorphic rocks are the third major type of rock, the other two being igneous and sedimentary.
75 429 954 900 162 276 875 178 107 210 807 701 575 168 698 614 1071 478 461 740 156 1428 668 1509 1395 147 728 685 999 1154 685 854 1387 1435 381 887 27 1083 1487