Metamorphic rocks form when rocks are subjected to high heat, high pressure, hot mineralrich fluids or, more commonly, some combination of these factors. Facies concept developed by eskola norway, 1915 to compare metamorphic rocks from different areas. The field of conditions of metamorphism is divided by approximately isothermal. Facies represent specific temperature pressure regimes. Mechanical deformation and chemical recrystallization are the two processes that affect rock during metamorphism. Atlas of metamorphic minerals university of oxford. Gallery of photographs of highgrade metamorphic rocks. Since new minerals are created during metamorphism, the end product metamorphic. 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 in nature shale to slate metamorphism deformation of sedimentary rocks metamorphic rocks record how temperature and pressure affected an area when it was forming.
Metamorphic rocks make up the largest volume of the earth. International listing of research groups working on metamorphic rocks and processes. During metasomatism the rock remains in a solid state. Rock types and metamorphic data largely match those of tvb basement unit. Metamorphic rocks are usually highly deformed because they have been subjected to high temperature and pressure. Diagenesis is sometimes divided into early and late phases. This new edition of petrogenesis of metamorphic rocks has several completely revised chapters and all chapters have updated references and redrawn. 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, metamorphic rocks, metamorphes gestein, gesteinsbildung, petrologie, petrogenese, roches metamorphiques, metamorphisme geologie. Mineral resources of igneous and metamorphic origin.
Normally a geothermal gradient increases in temperature with depth at about 30c per kilometer. Principles of igneous and metamorphic petrology second edition. The presence of index minerals in metamorphic rocks allows geologists to assess the temperatures and pressures the parent rock encountered. Mcdermott the basic terminology of igneous petrology. We classify these compositegenesis rocks according to descriptive properties that reflect the multiple processes that make the rock composite. All the rocks that have reached chemical equilibrium under a particular set of physical conditions. Texture in metamorphic rocks individual minerals may or may not be bounded by crystal faces. Metamorphic textures and mineralogy develop progressively over several hundreds of feetmeters of drilling. Metamorphic rocks form by solidstate no melting transformation of preexisting rock by processes that take place beneath earths surface.
Metamorphism is typically associated with elevated temperature and pressure, thus it affects rocks within the earths crust and mantle. Pelitic metamorphic rocks formed during regional metamorphism include many varieties of slate, phyllite, schist, and gneiss. Sedimentary rocks are formed from the cementing together of sediments, or from the compaction squeezing together of sediments, or from the recrystallization of. 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. Generally, metamorphic grade is closely associated with the maximum temperature of metamorphism so that highergrade rocks have experienced higher. Purchase petrology of metamorphic rocks, volume 9 1st edition. Rock metamorphism is a geological process that changes the mineralogical and chemical composition, as well as the structure of rocks. Diagenesis is the name for a wide range of changes that affect sediments during their progress to become sedimentary rocks. Deep underground rocks are exposed to high pressures from the overlying layers of rocks and high temperatures from magma. Rock metamorphism is always associated with processes and changes. They systematically change their mineralogical composition as a result of tectothermal events.
Second, it has implications for the texture of metamorphic rocks. 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. High pt metamorphic rocks 1brecommendations by the iugs subcommission on the systematics of metamorphic rocks. During metamorphism the protolith undergoes changes in texture of the rock and the mineral make.
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. 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. 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. 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. However, metamorphic rocks can form from metamorphic parent rocks as well. Exhumation where compression squeezes deep rock upward.
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 structural and metamorphic records in the pebbles are prepermian, and the conglomerate matrix is nonmetamorphic. The most obvious features of metamorphic rocks are certain planar features that are often termed ssurfaces. The process by which metamorphic rocks are produced is called metamorphism. Metamorphism involves changes in mineral assemblage and rock texture and occurs in the solid state as a result of changes in temperature and pressure. Outline the role of volatiles in metamorphic processes. Pdf petrogenesis of metamorphic rocks, 8th edition. Request pdf on jan 1, 2002, kurt bucher and others published petrogenesis of metamorphic rocks find, read and cite all the research you need on researchgate. Each of these will be discussed in turn, then we will summarize how metamorphic rocks are classified. The iugs mineralogical based classification and nomenclature scheme for phaneritic and aphanitic igneous rocks. 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.
A metamorphic rock is a result of a transformation of a preexisting rock. Right a metamorphic rock mylonite resulting from extreme deformation of granitic rocks. 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. The mineral paragenesis and metamorphic reactions described for carbonatesilicate rocks and impure marbles indicated that both group of rocks represent metamorphic product of. This planar fabric is characteristic of many metamorphic rocks. Metamorphic rocks that form because they are exposed to heat from magma form at the same plate boundaries igneous rocks form. As the rock crystallizes or recrystallizes under directed pressure, new crystals may grow in some preferred. Petrogenesis of metamorphic rocks presents a large number of diagrams showing the stability relations among minerals and groups of minerals found in metamorphic rocks. Methods for determining temperatures and pressures have become almost routine, and there is a wide appreciation that there is not a single temperature and pressure of metamorphism, but that.
Metamorphism reworks rocks in the earths crust and mantle. Classification of metamorphic rocks is based on mineral assemblage, texture, protolith, and bulk chemical composition of the rock. Geology of the north cascades scenic metamorphic rocks. 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. Metamorphic rocks are the third major type of rock, the other two being igneous and sedimentary. The x axis is temperature in celsius and the y axis is kilometers below the surface. Principles of igneous and metamorphic petrology second edition this textbook provides a basic understanding of the formative processes of igneous and metamorphic rocks through quantitative applications of simple physical and chemical principles. Origin, texture, and classification of metamorphic rocks.
They are formed when sedimentary and igneous rocks become changed by pressure and heat. For example, if slate is exposed to higher temperature and pressure, it will become a rock called schist. Phyllosilicates accommodate better shear other minerals dissolve due to high shear. Note the strong vertical fabric of the canyon wall. Rocks are formed on earth as igneous, sedimentary, or metamorphic rocks. The igneous rocks of the basement are granodiorites, tonalities, and some gabbros that cut the metamorphic basement and contain xenoliths and roof pendants from the country rocks. Seen on a global scale they constitute the dominant material of the earth. Like igneous rocks, metamorphic rocks almost exclusively form at plate boundaries. The outstanding feature of the 7th edition of this book is the large number of phase diagrams showing the stability relations among minerals and groups of minerals found in metamorphic rocks. Together, we will go through the following essential steps for a complete petrographic description of a metamorphic rock. Hand specimen and thin section description of igneous rocks.
Thus coarse grained metamorphic rocks involve long times of metamorphism. As the rock crystallizes or recrystallizes under directed pressure, new crystals may grow in some preferred direction, sometimes. These types of metamorphic rocks can also form at hot spots. Explain what an open and closed metamorphic system is. Classification and nomenclature of igneous rocks prof. Shock metamorphism when earth is struck by large meteoroids and the impact generate a compressional shock wave at extremely high pressure and heat forming craters. Discuss the mode of occurrence and characteristic textures common in metamorphic rocks. 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. The simplest planar features may be primary bedding akin to the layering in sedimentary rocks. The most typical metamorphism transforms sedimentary rocks to metamorphic rocks by addition of heat during mountain building or by a large volume of magma in the crust. We can measure the mineral compositions and assemblage i. Studies of metamorphic rocks provide insights into the physical and chemical changes that take place deep within earth.
It does not include weathering, the processes that turn all kinds of rock into sediment. Minerals and mineral assemblages originally not present in a rock may form, the new mineral assemblages grow at the expense of old ones. Pdf petrogenesis of metamorphic rocks download ebook for. Some types of metamorphic rocks, such as quartzite and marble, which can form whether there is directedpressure or not, do not typically exhibit foliation because. Knowledge of metamorphic processes and rocks is valuable, because metamorphic. The book encourages a deeper comprehension of the subject by explaining the. As per wikipedia, metamorphic rocks arise from the transformation of existing rock types, in a process called metamorphism, which means change in form. Bucher and others published petrogenesis of metamorphic rocks 8th edition find, read and cite all the research you need on researchgate. Agents of metamorphism heat pressure chemical activity heat is the most important agent of metamorphism. The mineral paragenesis and metamorphic reactions described for carbonatesilicate rocks and impure marbles indicated that both group of rocks represent metamorphic product of marls andor silt. Grade of metamorphism metamorphic grade is a general term for describing the relative temperature and pressure conditions under which metamorphic rocks form. 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.
Metamorphic rock type with basalt or gabbro protolith. Metamorphism and metamorphic rocks tulane university. For example, slate and marble are building materials, garnets are used as gemstones. Chemical, mineralogical and structural adjustments of solid rocks to physical and chemical changes at depths below the region of sedimentation. Rocks caught in the action are heated, squeezed, and sheared creating foliated rocks. 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. The diagrams help to determine the pressure and temperature conditions under which a given set of metamorphic rocks may have formed. 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. Are rich in fe and mg and turn into amphiboledominated rocks. Many precious materials, such as marble and many types of gemstones, including diamonds, are formed by the metamorphic process.
The understanding of the petrogenesis and significance of metamorphic of geological education. Lightcolored dikes and sills of igneous rock cut the metamorphic rocks. Principles of igneous and metamorphic petrology second. Rocks that are subjected to very high confining pressures are typically denser than others because the mineral grains are squeezed together figure 7. The rocks provide clues to their transformation into a metamorphic rocks. Igneous rocks form when rocks are heated to the melting point which forms magma. Petrology of metamorphic rocks, volume 9 1st edition. 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. 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. Petrogenesis of metamorphic rocks 8th edition request pdf. Also, the chapters introduction and grade have undergone several major changes.
Metamorphic rocks are one of the three classes of rocks. Because of how they are formed, metamorphic rocks constitute a great deal of the bedrock in earths crust. Igneous rocks as igneous rocks form out of magma and lava from the interior of the earth, they are known as primary rocks. Concise information about metamorphic processes, with excellent cartoon of mineral growth during compression.
Summarize the progression of different rock types produced by regional. Experiments suggest that the time involved is tens of millions of years. 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. Metamorphic rocks are best identified when looking at the rock as you see them in nature. Metamorphic rocks started out as some other type of rock, but have been substantially changed from their original igneous, sedimentary, or earlier metamorphic form.