Gneiss rocks exhibit a unique form of foliation known as gneissic banding, which are thicker bands of foliation than most metamorphic rocks display. Twelve multi-authored sections explain how to derive the correct names for metamorphic rocks and processes, and discuss the rationale behind the more important terms. Igneous rocks are formed when magma cools and solidifies. 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. TY - JOUR. Schematic cross section through a shear zone, showing the vert ical distribution of fault -related rock types, ranging from non -cohesive gouge and breccia near the surface through progressivel y more cohesive and foliated rocks. Rock Classification. The "metamorphic index" (MI) is introduced as an estimator of average metamorphic grade of source rocks. Most metamorphic rocks that we observe at Earth’s surface were derived from the three most common sedimentary rocks—shale, limestone, and quartz sandstone. They cannot be covered by a simple scheme of classification, but a simple textural classification is given below. It presents a complete nomenclature of metamorphic rocks, with a comprehensive glossary of definitions, sources and etymology of over 1200 terms, and a list of mineral abbreviations. The preexisting rocks may be igneous, sedimentary, or other metamorphic rocks. Metamorphic Rock Classification High Strain Rocks Figure 22 -2 . It is one of the features that helps differentiate gneiss from other foliated rocks. The change might have been due to an increase in temperature or pressure or both. Foliated Metamorphic Rocks 2. They may originate by injection (injection migmatite, injection gneiss, or lit-par-lit gneiss) or by differential fusion. Metamorphic rocks form from pre-existing rocks ("parent rocks") due to changes in either temperature, pressure, or volatiles within the earth, often by a combination of all three. Metamorphic rocks are classified by their texture, which is either foliated or non-foliated, and according to their parent rock. Classification of Metamorphic Rocks 1. These rocks have a gneissose, streaked, or irregular structure produced by intimate mixing of metamorphic and magmatic materials. TEXTURES Textures of metamorphic rocks fall into two broad groups, FOLIATED and NON-FOLIATED. Examples: Slate, Schist, Gneiss, etc. One is that it formed under conditions that did not include a directed pressure -- it is either a contact or a deep-burial metamorphic rock. AU - Nasir, S. PY - 1993. 7.2 Classification of Metamorphic Rocks There are two main types of metamorphic rocks: those that are foliated because they have formed in an environment with either directed pressure or shear stress, and those that are not foliated because they have formed in an environment without directed pressure or relatively near the surface with very little pressure at all. Slates are characterized by the ‘presence of numerous closely- spaced parallel planes of […] ‘metamorphic rock’ in this classification. Classification Of Metamorphic Rocks. Metamorphic RocksMetamorphic Rocks FORMED BY HEAT ANDFORMED BY HEAT AND PRESSUREPRESSURE 2. OLDER ROCKS MAY BEOLDER ROCKS MAY BE FORMED INTO A NEW TYPEFORMED INTO A NEW TYPE OF METAMORPHIC ROCKOF METAMORPHIC ROCK 3. When sedimentary rocks or igneous rocks go through the physical process such as pressure exposure, heat changes, and tectonic plate movement at … FOLIATED METAMORPHIC ROCKS. Metamorphic rock, any of a class of rocks that result from the alteration of preexisting rocks in response to changing environmental conditions, such as variations in temperature, pressure, and mechanical stress, and the addition or subtraction of chemical components. Metamorphic Rocks: A Classification and Glossary of Terms: Recommendations of the International Union of Geological Sciences Subcommission on the Systematics of Metamorphic Rocks | Douglas Fettes, Jacqueline Desmons | ISBN: 9780521868105 | Kostenloser Versand für alle Bücher mit Versand und Verkauf duch Amazon. Cataclastic rock, impact-metamorphic rock, and composite-genesis melt rocks are treated as special classes. Figure \(\PageIndex{1}\): Igneous rock classification table with composition as vertical columns and texture as horizontal rows. They are: ADVERTISEMENTS: (a) Foliated rocks: This group includes the rock that can split into thin sheets. Classification of rocks Rocks found on the Earth's surface come from inside the Earth, telling us a lot about the Earth's interior. Go back to start of main content Go back to top of page . Textural Classification of Metamorphic Rocks: Since metamorphic rocks can be formed from any type of existing rocks, their mineral composition ranges more widely than that of all other types of rock. Nature rarely has sharp boundaries and the classification and naming of rocks often impose what appears to be sharp boundary names onto a continuous spectrum. Granite from Cape Cod, … They make up the crust of the Earth and are found on the surface of the Earth. 1. Classification of Metamorphic Rocks. Classification of igneous rocks. While metamorphic rocks can be formed in different ways, the resulting rocks can also be categorized based on the way in which minerals align in the newly formed rock. 6.2 Classification of Metamorphic Rocks There are two main types of metamorphic rocks: those that are foliated because they have formed in an environment with either directed pressure or shear stress, and those that are massive (not foliated) because they have formed in an environment without directed pressure or relatively near the surface with very little pressure at all. 7.2 Classification of Metamorphic Rocks. Structures in Metamorphic Rocks 3. Discover more. There are two reasons that a metamorphic rock might not have any foliation. They are classified by using grain size, silica content, and/or silica saturation. Non-Foliated Metamorphic Rocks. CLASSIFICATION OF METAMORPHIC ROCKS. Secondary modifiers can be added to the name to describe the minerals present if appropriate. T1 - Classification and nomenclature of metamorphic rock. There are two main types of metamorphic rocks: those that are foliated because they have formed in an environment with either directed pressure or shear stress, and those that are not foliated because they have formed in an environment without directed pressure or relatively near the surface with very little pressure at all. Greenish rocks that form in this way (containing chlorite) are called GREENSTONE. These rocks are classified as either foliated or non foliated rocks. METAMORPHIC CLASSIFICATION Foliation is produced in a rock by the parallel alignment of platy minerals (e.g., muscovite, biotite, chlorite), needle-like minerals (e.g., hornblende), or tabular minerals (e.g., feldspars). NON-FOLIATED ROCKS. Chapter 22 A Classification of Metamorphic Rocks A good name is a concise way of imparting information about a rock 2. Metamorphic Classification - Copy - View presentation slides online. Rock Classification Scheme Volume 2: metamorphic rocks Volume 3: classification of sediments and sedimentary rocks Existing sediment and sedimentary rock nomenclature has been based on composition, texture and other physical attributes as well as depositional environment, genetic relationships and local economic importance. Metamorphic rocks are formed when rock changes over a period of time due to a lot of physical changes like pressure, heat and different chemical activity. Beginning in the 18th century, geologists struggled to develop a sensible way to classify rocks, for they realized, as did miners from centuries past, that not all rocks are the same. (iii) Metamorphic Rocks: This rock type is originally either igneous rocks or sedimentary rocks which have undergone some change in their structure, shape or composition. Gneiss is a foliated metamorphic rock. Rocks are all around us. Buy Metamorphic Rocks (9780521336185) (9780521868105): A Classification and Glossary of Terms: NHBS - Edited By: Douglas Fettes and Jacqueline Desmons, Cambridge University Press Slate: Slates are formed due to dynamic regional metamorphism of shales and other argillaceous rocks. When they can be recognized as "mixed rock," they are called migmatite or migmatite gneiss. Engineering Uses. Y1 - 1993. You have reached the end of the main content. Mineralogically, tends to include quartz, feldspar, mica, chlorite, and other clay minerals. Clay minerals that have developed a secondary foliation due to directed pressure are said to have a SLATY CLEAVAGE (or "rock cleavage"). Sometimes, the change is due to some chemically active fluids that act on the pre-existing rocks. Rocks: Igneous, Metamorphic and Sedimentary Rocks hold the history of the earth and the materials that will be used to build its future. Classification of Metamorphic Rocks: 1. Classification of Metamorphic Rocks 2. Aphanitic/Phaneritic Rock Types with Images . ADVERTISEMENTS: Metamorphic rocks are classified on the basis of foliation into the following types: 1. UNESCO – EOLSS SAMPLE CHAPTERS GEOLOGY – Vol. Classification schemes help us organize information and remember significant details about materials or objects, and they help us recognize similarities and differences among them. As per Wikipedia, “”Metamorphic rocks arise from the transformation of existing rock types, in a process called metamorphism, which means “change in form””.The original rock (protolith) is subjected to heat (temperatures greater than 150 to 200 °C) and pressure (1500 bars), causing profound physical and/or chemical change. Metamorphic Rocks: A Classification and Glossary of Terms: Recommendations of the International Union of Geological Sciences Subcommission on the Systematics of Metamorphic Rocks: Amazon.de: Fettes, Douglas: Fremdsprachige Bücher Metamorphic rocks may be classified on the basis of foliation into two types. Volatiles are those chemical substances, including water and carbon dioxide, that easily turn into gas or fluid and are mobile enough to move in and out of solid rock inside the earth. Felsic Composition. Foliated Rocks Gneiss rock with red veins. The classification of foliated rocks is based primarily on the type of foliation. Chapter 22: A Classification of Metamorphic Rocks Chapter 22: A Classification of Metamorphic Rocks Additional Modifying Terms: Other modifying terms that we may want to add as a means of emphasizing some aspect of a rock may concern such features as grain-size, color, chemical aspects, (aluminous, calcareous, mafic, felsic, etc.). Foliated Metamorphic Rocks: i.
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