Thus coarse grained metamorphic rocks involve long times of metamorphism. In reality the spatial relationship between the stress axes and structure is not. Agents of metamorphism heat pressure chemical activity heat is the most important agent of metamorphism. Learn to identify metamorphic rocks by structure and mineralogy. Because of how they are formed, metamorphic rocks constitute a great deal of the bedrock in earths crust. Slate phyllite schist gneiss parent rocks can vary shale, siltstone, granite, etc. All the rocks described in this spread are foliated. 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. Metamorphism involves changes in mineral assemblage and rock texture and occurs in the solid state as a result of changes in temperature and pressure. 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.
Change is a result of pressure directed stress and heat solid state reaction no net change in chemistry ideally role of groundwater recrystallization of. This confining pressure increases in proportion to the depth of burial. Stages of metamorphism foliated rocks slate schist gneiss gneiss stripes. 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. 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. 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. Many precious materials, such as marble and many types of gemstones, including diamonds, are formed by the metamorphic process. Pdf stable isotope geochemistry of metamorphic rocks.
Together, we will go through the following essential steps for a complete petrographic description of a metamorphic rock. 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. Metamorphic rock metamorphic rock structural features. Metamorphic textures and mineralogy develop progressively over several hundreds of feetmeters of drilling. Rocks change due to heat, weatheringerosion, and cooling, and pressure earth is like one big rock recycling machine. Grade of metamorphism metamorphic grade is a general term for describing the relative temperature and pressure conditions under which metamorphic rocks form. The preexisting rocks may be igneous, sedimentary, or other metamorphic rocks. Protolith original rock type before metamorphism metamorphism is typically indicated by change in mineral type, change in texture, or foliation. Pdf structure and metamorphism of rocks as a criterion of. Metamorphic flagstones are characterised by a regularly spaced mica foliation separated by quartzofeldspathic domains, along which the rocks can be cleaved.
Metamorphic differentiation rocks are inhomogeneous so is the deformation in rocks experiencing shear separation of high and low shear zones by transition zones. Note the strong vertical fabric of the canyon wall. Since new minerals are created during metamorphism, the end product metamorphic. In many cases, the correlation of metamorphic isograds and their position in the structure implies a genetic relationship. Foliated rocks produced by regional metamorphism these rocks have all been affected by pressure, to some degree, during regional metamorphism. Metamorphic rocks that are classified according to texture include slate, phyllite, schist, and gneiss. 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 electronic textbook. In this activity, students will be asked to identify a number of common metamorphic rocks using the enclosed sheets.
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. For example, if slate is exposed to higher temperature and pressure, it will become a rock called schist. We can measure the mineral compositions and assemblage i. Gneissose structure and layers rocks having alternate light and dark layers.
Amphibolite, marble, and quartzite are defined according to their composition. Metamorphic rock names based on parent rock, geologic setting, and metamorphic grade. Metamorphic rocks form gradually from existing rocks in solid state, so they remain rocks throughout the process. Metamorphic rocks are identified by their textures as their textures can tell us a lot about the overall conditions of metamorphism. 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.
Metamorphic rocks may be classified on the basis of foliation into two types. Deformationmetamorphic structure, texture and geothermometry of graphitic carbonbearing rocks within ailaoshan metamorphic complex. All chapters of part ii of the book have been rewritten. They are formed when sedimentary and igneous rocks become changed by pressure and heat. The foliation is usually perpendicular to the direction of the applied stress. Explain what an open and closed metamorphic system is. Metamorphic rocks are the third major type of rock, the other two being igneous and sedimentary.
Any existing open space between mineral grains in a rock can potentially contain a fluid. Lightcolored dikes and sills of igneous rock cut the metamorphic rocks. Parent rocks the rock that the metamorphic rock comes from. 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. 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. Summarize the progression of different rock types produced by regional. Metamorphic changes do not involve melting higher temperatures are needed for that, nor any change to the chemical composition of the rock. In this hand specimen of vermont marble, the crystals are small. Identify major minerals contained within a metamorphic rock. The major features of metamorphic rocks that can be widely used for classification are. This type of metamorphic rock consists of recrystallized calcite in limestone or dolomite in dolomite rock. 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. Metamorphic rocks are usually highly deformed because they have been subjected to high temperature and pressure. 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.
Structure and metamorphism of rocks as a criterion of dissection and correlation of polymetamorphic complexes on example of the subpolar urals. Read this sciencestruck article to gain extensive information about the main features of these rocks. As per wikipedia, metamorphic rocks arise from the transformation of existing rock types, in a process called metamorphism, which means change in form. Deformationmetamorphic structure, texture and geothermometry of. Textural features of metamorphic rocks have been discussed in the previous. 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. Origin, texture, and classification of metamorphic rocks. Metamorphic rocks have had their appearance texture and mineral composition changed because of intense heat andor pressure. Skarn, hornfels, and migmatite are classified according to their genesis. Metamorphism and metamorphic rocks chapter questions. Additionally, if you would like all of the resources together in a pdf document, that can be accessed as a complete resource here. The chart below summarizes the parent rock, setting, and grade of common metamorphic rocks. 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.
Classification of metamorphic rocks based on texture mj college. Discuss the mode of occurrence and characteristic textures common in metamorphic rocks. 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. Mechanical deformation and chemical recrystallization are the two processes that affect rock during metamorphism. 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. Metamorphism and metamorphic rocks metamorphism mineralogical, chemical, and physical changes that occur in solid rocks.
However, metamorphic rocks can form from metamorphic parent rocks as well. Such features include folds, nappes, and faults with a wide variety of geometries. 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. Classification of metamorphic rocks depends on what is visible in the rock and its degree of metamorphism. 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. Petrography the branch of geology dealing with the description and systematic classification of rocks, especially by microscopic examination of thin sections. Deep underground rocks are exposed to high pressures from the overlying layers of rocks and high temperatures from magma. Textures and structures of metamorphic rocks and various mechanisms behind the. 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. Metamorphic processes and products flashcards quizlet. Characteristics of metamorphic rocks science struck. 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.
Students should work in groups of two or three, each group will need. It is considered to be an excellent building material for important monumental. 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. The metamorphic rocks are extensively used as building stones. 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. This new edition of petrogenesis of metamorphic rocks has several completely revised chapters and all chapters have updated references and redrawn.
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. 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. The rock cycle it is how earth changes one type of rock into another type of rock. Phyllosilicates accommodate better shear other minerals dissolve due to high shear. Migrate to low shear area, where porphyroblasts form. Metamorphic rocks are identified based on grain size, mineral composition, and texture see the accompanying chart. 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. Any platy minerals they contain take on a preferred alignment known as foliation. All rocks are under pressure as a result of burial. Experiments suggest that the time involved is tens of millions of years. Metamorphic rocks can change into another metamorphic rock.
Metamorphic comes from the greek word meta and morph, meaning change in form. Textures and structures of metamorphic rocks slideshare. Also, the chapters introduction and grade have undergone several major changes. 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. Metamorphism and metamorphic rocks tulane university. We classify these compositegenesis rocks according to descriptive properties that reflect the multiple processes that make the rock composite. Metamorphic rocks are often intimately related to largescale kilometres of tens of kilometres structural features of earth. Eighth grade lesson metamorphic rocks i betterlesson.