The chart below summarizes the parent rock, setting, and grade of common metamorphic rocks. 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. Migrate to low shear area, where porphyroblasts form. This type of metamorphic rock consists of recrystallized calcite in limestone or dolomite in dolomite rock. For example, if slate is exposed to higher temperature and pressure, it will become a rock called schist. Nonfoliated metamorphic rocks do not typically have a planar structure no foliation these metamorphic rocks are produced in environments where directed stresses are minimal i. Summarize the progression of different rock types produced by regional. All the rocks described in this spread are foliated. Gneissose structure and layers rocks having alternate light and dark layers. Metamorphic rock names based on parent rock, geologic setting, and metamorphic grade.
Marble is made by regional metamorphism of limestone or dolomite rock, causing their microscopic grains to combine into larger crystals. However, metamorphic rocks can form from metamorphic parent rocks as well. 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. 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. Metamorphism and metamorphic rocks rocks created by heat, pressure andor chemically reactive fluids metamorphic rocks are produced from igneous rocks sedimentary rocks other metamorphic rocks 2. Students should work in groups of two or three, each group will need. Metamorphic rocks that are classified according to texture include slate, phyllite, schist, and gneiss.
Classification of metamorphic rocks depends on what is visible in the rock and its degree of metamorphism. The rock cycle it is how earth changes one type of rock into another type of rock. Metamorphism and metamorphic rocks tulane university. Additionally, if you would like all of the resources together in a pdf document, that can be accessed as a complete resource here.
The metamorphic rocks are extensively used as building stones. Skarn, hornfels, and migmatite are classified according to their genesis. Structure and metamorphism of rocks as a criterion of dissection and correlation of polymetamorphic complexes on example of the subpolar urals. This planar fabric is characteristic of many metamorphic rocks. Metamorphic settings b, r, s b, r, s s b, r, s b, r, s parent rock shale granite basalt chert sio2 limestone. Examples from cornwall that show the first tectonic and metamorphic fabrics in metasediments, plus a variety of sedimentary and igneous rock types in outcrop and hand specimen. Grade of metamorphism metamorphic grade is a general term for describing the relative temperature and pressure conditions under which metamorphic rocks form. In many cases, the correlation of metamorphic isograds and their position in the structure implies a genetic relationship. This confining pressure increases in proportion to the depth of burial. Lightcolored dikes and sills of igneous rock cut the metamorphic rocks.
Metamorphic rocks have had their appearance texture and mineral composition changed because of intense heat andor pressure. Classification of metamorphic rocks based on texture mj college. Any existing open space between mineral grains in a rock can potentially contain a fluid. The zonal distribution of rocks showing different degrees of metamorphism in those metamorphic terranes that have been studied in detail is attributed to progressive variation in physical conditions controlling development of a state of internal equilibrium in rocks of varying composition in different chemical environments. Read this sciencestruck article to gain extensive information about the main features of these rocks. Metamorphic comes from the greek word meta and morph, meaning change in form.
In this hand specimen of vermont marble, the crystals are small. 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. If the schist is exposed to even higher temperature and pressure, it will become gneiss a different kind of gneiss than the granitic gneiss because slate is its. Textures and structures of metamorphic rocks slideshare. Deformationmetamorphic structure, texture and geothermometry of graphitic carbonbearing rocks within ailaoshan metamorphic complex. Also, the chapters introduction and grade have undergone several major changes. Slate phyllite schist gneiss parent rocks can vary shale, siltstone, granite, etc. They are formed when sedimentary and igneous rocks become changed by pressure and heat. In reality the spatial relationship between the stress axes and structure is not.
In this activity, students will be asked to identify a number of common metamorphic rocks using the enclosed sheets. Identify major minerals contained within a metamorphic rock. Metamorphic rocks may be classified on the basis of foliation into two types. Metamorphic rocks revised on 1082012 page 2 of 9 igneous rocks form from magma, which is not a rock since it is a fluid and sedimentary rocks lithify from loose sediment or precipitate from a solution. Agents of metamorphism heat pressure chemical activity heat is the most important agent of metamorphism. 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. Petrography the branch of geology dealing with the description and systematic classification of rocks, especially by microscopic examination of thin sections. Metamorphic textures and mineralogy develop progressively over several hundreds of feetmeters of drilling. Note the strong vertical fabric of the canyon wall. Stages of metamorphism foliated rocks slate schist gneiss gneiss stripes.
Metamorphic rocks are former igneous, sedimentary or metamorphic rocks that have changed their texture and composition. Their study provides us with important data regarding formation of the earth and the past geological environment. Amphibolite, marble, and quartzite are defined according to their composition. Metamorphic rocks can change into another metamorphic rock. Metamorphic rock metamorphic rock structural features. Mechanical deformation and chemical recrystallization are the two processes that affect rock during metamorphism. 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. Outline the role of volatiles in metamorphic processes. Metamorphic rocks are identified by their textures as their textures can tell us a lot about the overall conditions of metamorphism. Since new minerals are created during metamorphism, the end product metamorphic. Metamorphic processes and products flashcards quizlet. Slaty cleavage rocks with slaty cleavage will split into thin sheets along the cleavage planes and occurs in fine grained rock formed by low grade regional metamorphism.
Geochemical characteristic of metamorphic rocks from south sulawesi, central java, south and west kalimantan in indonesia nugroho imam setiawan1, yasuhito osanai2, nobuhiko nakano3, tatsuro adachi4, kazuhiro yonemura5, aya yoshimoto6, lucas donny setiadji7, kaharuddin mamma8, joko wahyudiono9 1,2,3,4,5,6division of earth sciences, faculty of social and cultural. One of the oldest types of rocks on our planet, metamorphic rocks are mainly formed due to changes in the parameters of temperature and pressure, which act on the parent material. Process of mineralogical and structural textural changes of rocks in the solid state in response to physical and chemical conditions which differ from those under which they originated. Foliated metamorphic rocks can be broadly classified by type of foliation and parent rock composition less important as metamorphic grade t and p increases, rock type will change. Metamorphic rocks are often intimately related to largescale kilometres of tens of kilometres structural features of earth. Injection of the these melts into pods and layers in the rock could also produce the discontinuous banding often seen in high grade metamorphic rocks. Explain what an open and closed metamorphic system is. Deformationmetamorphic structure, texture and geothermometry of. Experiments suggest that the time involved is tens of millions of years. At great depths, the pressure is sufficient to cause recrystallization along grain boundaries, but because confining pressure is the same in all directions, mineral grains grown under these conditions of uniform stress do not have a preferential growth direction.
Any platy minerals they contain take on a preferred alignment known as foliation. 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 separated from its. Origin, texture, and classification of metamorphic rocks. It is considered to be an excellent building material for important monumental.
Textures and structures of metamorphic rocks and various mechanisms behind the. Metamorphism and metamorphic rocks chapter questions. Metamorphic differentiation rocks are inhomogeneous so is the deformation in rocks experiencing shear separation of high and low shear zones by transition zones. We classify these compositegenesis rocks according to descriptive properties that reflect the multiple processes that make the rock composite. Metamorphic rocks form gradually from existing rocks in solid state, so they remain rocks throughout the process. Protolith original rock type before metamorphism metamorphism is typically indicated by change in mineral type, change in texture, or foliation. Finally, students may need their earth science reference tables esrt for parts of the lesson a document used widely in the new york state earth science. Learn to identify metamorphic rocks by structure and mineralogy. The foliated rocks like slate, gneiss and schist are used as roofing material tabletops, staircases, etc. All chapters of part ii of the book have been rewritten. Metamorphic flagstones are characterised by a regularly spaced mica foliation separated by quartzofeldspathic domains, along which the rocks can be cleaved. The preexisting rocks may be igneous, sedimentary, or other metamorphic rocks. Metamorphic rocks are the third major type of rock, the other two being igneous and sedimentary. Metamorphic rocks and processes metamorphism comes from the greek words meta change morphe form metamorphic rocks form by solidstate no melting transformation of preexisting rock by processes that take place beneath earths surface.
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. Phyllosilicates accommodate better shear other minerals dissolve due to high shear. Together, we will go through the following essential steps for a complete petrographic description of a metamorphic rock. Metamorphic changes do not involve melting higher temperatures are needed for that, nor any change to the chemical composition of the rock. Metamorphism involves changes in mineral assemblage and rock texture and occurs in the solid state as a result of changes in temperature and pressure. Eighth grade lesson metamorphic rocks i betterlesson. Metamorphism and metamorphic rocks metamorphism mineralogical, chemical, and physical changes that occur in solid rocks. We can measure the mineral compositions and assemblage i. As per wikipedia, metamorphic rocks arise from the transformation of existing rock types, in a process called metamorphism, which means change in form. Parent rocks the rock that the metamorphic rock comes from. Pdf stable isotope geochemistry of metamorphic rocks. The lab is designed to model the methodology involved in describing a metamorphic thinsection thoroughly, thereby allowing you to name rock and interpret its history or mineral growth paragenetic sequence. Such features include folds, nappes, and faults with a wide variety of geometries. Discuss the mode of occurrence and characteristic textures common in metamorphic rocks.
Metamorphic rocks metamorphic rocks are rocks from sedimentary and igneous origin that have been changed through high pressures and temperatures during orogenesis mountain building or during igneous intrusion contact metamorphism metamorphic rocks cont. Textural features of metamorphic rocks have been discussed in the previous. Occurs at depths greater than where sedimentary rocks form. Change is a result of pressure directed stress and heat solid state reaction no net change in chemistry ideally role of groundwater recrystallization of. All rocks are under pressure as a result of burial. Foliated rocks produced by regional metamorphism these rocks have all been affected by pressure, to some degree, during regional metamorphism.
The process would be similar to that described in 4, above, except that it would involve partially melting the original rock to produce a felsic melt, which would then migrate and crystallize in pods and layers in the metamorphic rock. Metamorphic rocks are usually highly deformed because they have been subjected to high temperature and pressure. Characteristics of metamorphic rocks science struck. Thus coarse grained metamorphic rocks involve long times of metamorphism. Pdf structure and metamorphism of rocks as a criterion of. The foliation is usually perpendicular to the direction of the applied stress. This new edition of petrogenesis of metamorphic rocks has several completely revised chapters and all chapters have updated references and redrawn. Deep underground rocks are exposed to high pressures from the overlying layers of rocks and high temperatures from magma. 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. The major features of metamorphic rocks that can be widely used for classification are. Foliated metamorphic rocks form under directed pressure pressure that is not the same in all directions or shear stress forces acting parallel to each other, and having the result of smearing the rock.
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