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Topic: Metamorphism


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In the News (Mon 15 Jul 19)

  
  Metamorphic Rocks
Metamorphic grade is a general term for describing the relative temperature and pressure conditions under which metamorphic rocks form.
Within increasing pressure of metamorphism, the pore spaces in which the fluid resides is reduced, and thus the fluid is driven off.
The sequence of metamorphic facies observed in any metamorphic terrain, depends on the geothermal gradient that was present during metamorphism.
www.tulane.edu /~sanelson/geol111/metamorphic.htm   (2193 words)

  
  Metamorphism - Wikipedia, the free encyclopedia
Metamorphic facies are recognizable terranes or zones with an equilibrium assemblage of key minerals that were in equilibrium under specific range of temperature and pressure during a metamorphic event.
As expected, the contact metamorphic effects are greater adjacent to the intrusive rock and fade away toward the exterior of the aureole.
Hydrothermal metamorphism is the result of the interaction of a rock with a high-temperature fluid of variable composition.
en.wikipedia.org /wiki/Metamorphism   (722 words)

  
 Metamorphic rock - Wikipedia, the free encyclopedia
Metamorphic rock is the result of the transformation of a pre-existing rock type, the protolith, in a process called metamorphism, which means "change in form" (from the Greek words meta, "change", and morphe, "form").
Metamorphic rocks make up a large part of the Earth's crust and are classified by texture and by chemical and mineral assembly (metamorphic facies).
For instance, the small calcite crystals in the sedimentary rock limestone change into larger crystals in the metamorphic rock marble, or in metamorphosed sandstone, recrystallisation of the original quartz sand grains results in very compact quartzite, in which the often larger quartz crystals are interlocked.
en.wikipedia.org /wiki/Metamorphic_rock   (997 words)

  
 Metamorphic Rocks
Metamorphic rocks are consequently rocks that have undergone a change or "metamorphosis" from a previous state as a sedimentary, igneous or even another metamorphic rock.
Metamorphism is typically restricted to a thin "aureole" between 1 - 2 km wide adjacent to the pluton or batholith.
Metamorphic rocks are named primarily on the basis of their textures and grain size.
darkwing.uoregon.edu /~jrice/geol_311/Metamorphic.html   (2720 words)

  
 Types of Metamorphism
Classification of metamorphic rocks is based on mineral assemblage, texture, protolith, and bulk chemical composition of the rock.
From examination of metamorphic rocks, it has been found that metamorphic minerals can be listed in a generalized sequence, known as the crystalloblastic series, listing minerals in order of their tendency to be idioblastic.
As the grade of metamorphism increases, original textures are replaced with metamorphic textures and other clues, such as bulk chemical composition of the rock, are used to determine the protolith.
www.tulane.edu /~sanelson/geol212/typesmetamorph.htm   (2469 words)

  
 Metamorphic Rocks (Geo302)/ S. Nasir
Metamorphic rocks are derived from materials of igneous, sedimentary or metamorphic rocks by changing their physical form and /or mineralogical composition as a result of changes in pressure and /or temperature or by the effect of a fluid phase.
Metamorphism occurs in the solid state and is bounded by sedimentary diagenesis and igneous melting.
Metamorphism, in general, refers to the reactions between minerals of a rock in response to conditions of temperature and pressure prevailing at depth.
www.angelfire.com /ms/snasir/page7.html   (2647 words)

  
 METAMORPHISM (Gr. ise-... - Online Information article about METAMORPHISM (Gr. ise-...
Moreover, the degree of metamorphism in the rock can often be shown to correspond closely to the extent to which it has been folded and crushed.
It is almost equally certain that metamorphism must be accompanied by a rise of temperature in nearly every caseā€”in fact it is difficult to imagine such a process going on without considerable heat.
The metamorphism would then be partly of the contact type and partly the effect of pressure and movement, " pressure-contact-metamorphism." The vapours already present would be augmented by those given out from the igneous rock, and intensely crystalline, foliated masses, often containing minerals found in contact zones (andalusite, cordierite, sillimanite, staurolite, andc.), would be produced.
encyclopedia.jrank.org /MEC_MIC/METAMORPHISM_Gr_ise_rci_change_.html   (8270 words)

  
 Towards a Creationist explanation of regional metamorphism
Some of these metamorphic minerals have been found with remnants of their precursor materials alongside, the two coexisting in rocks that are supposed to have experienced the highest ‘grade’ of metamorphism.
Thus it is feasible to conclude that the classical zones of regional metamorphism represent zonal patterns of the original sedimentation, and that the precursor clay and associated minerals have undergone transformation to metamorphic mineral assemblages at low to moderate temperatures and pressures.
On the intrusion of muscovite-biotite gneiss in the southeastern Highlands of Scotland, and its accompanying metamorphism.
www.answersingenesis.org /tj/v8/i1/metamorphism.asp   (14207 words)

  
 10(g) Characteristics of Metamorphic Rocks   (Site not responding. Last check: 2007-10-26)
Metamorphism involves the alteration of existing rocks by either excessive heat and pressure, or through the chemical action of fluids.
Regional metamorphism is the large scale heating and modification of existing rock through the creation of plutons at tectonic zones of subduction.
Marble is a nonfoliated metamorphized limestone or dolomite).
www.physicalgeography.net /fundamentals/10g.html   (883 words)

  
 metamorphism on Encyclopedia.com
METAMORPHISM [metamorphism] in geology, process of change in the structure, texture, or composition of rocks caused by agents of heat, deforming pressure, shearing stress, hot, chemically active fluids, or a combination of these, acting while the rock being changed remains essentially in the solid state.
Further higher-grade metamorphic conditions lead to a foliation called schistosity, resulting in schists, formed when tabular minerals, such as hornblende, graphite, mica, or talc are aligned and tightly packed in a parallel fashion.
Metamorphic rocks that develop by shearing and crushing of the rock at low temperature are called cataclastic and are usually associated with the mechanical forces, especially pressure, involved in faulting (see fault).
www.encyclopedia.com /html/m1/metamorpsm.asp   (831 words)

  
 Metamorphism and Metamorphic Rocks
Metamorphism repesents the set of processes by which rocks undergo solid-state changes in mineralogy, texture, or both to reach equilibrium with its changing environment, generally as they are buried beneath the surface.
Metamorphic rocks are found in mountain ranges, roots of mountain ranges, and on continental shields (the stable cores of continents that contain the oldest known rocks, 3.96 billion years old).
Metamorphism is associated with all 3 types of plate boundaries, but is most common at convergent plate margins.
www.geo.ua.edu /intro03/Meta.html   (981 words)

  
 Kinds of Metamorphism
The intensity of metamorphism decreases with distance from the intrusion, until at some distance away the rock is unaltered country rock.
The metamorphism often occurs in aureoles, or zones surrounding the intrusion.
Barrovian metamorphism produces some of the most common metamorphic rocks, many of which are spectacularly beautiful and thus used as building stones.
csmres.jmu.edu /geollab/Fichter/MetaRx/MetaKind.html   (879 words)

  
 METAMORPHISM - LoveToKnow Article on METAMORPHISM   (Site not responding. Last check: 2007-10-26)
Where the degree of metamorphism is not too high, and the folding and dislocation not too complex, the sandstones, shales and limestones may be mapped out, and igneous bosses, dikes and sills, with their contact aureoles, veins, pegmatites and segregations, convincingly delineated on the maps.
The metamorphism in a rock series may be of nearly uniform intensity over a large area; the sediments, for example, may have all their clastic and organic structures effaced, and in the igneous rocks the porphyritic, ophitic, graphic and other textures may have completely disappeared.
In many metamorphic rocks we find hard minerals possessing little cleavage (such as quartz) reduced to an exceedingly fine state of division, and it is clear that the stresses which have acted on regions of metamorphic rocks are often so powerful that all the minerals may have been completely shattered.
www.1911ency.org /M/ME/METAMORPHISM.htm   (7998 words)

  
 Barrovian metamorphism
Barrovian metamorphism is widely found across time and space on all parts of the earth, and produces the most common metamorphic rocks.
Metamorphism is not rocks, it is a process - a process of burial, heat, and pressure.
They are index minerals because they index when, during the metamorphic processes, a particular set of temperature and pressure conditions have been achieved, and they appear in a set order: chlorite, biotite, garnet, staurolite, kyanite, and sillimanite.
csmres.jmu.edu /geollab/Fichter/MetaRx/Barrovian.html   (1177 words)

  
 Metamorphism   (Site not responding. Last check: 2007-10-26)
Metamorphism is defined as the mineralogical, chemical and structural adjustments in solid rocks to physical and chemical conditions which have been imposed due to changes in pressure and temperature or both.
Conditions of metamorphism differ from the conditions under which the rocks in question were originally formed.
Metamorphism produced as a result of the progressive increase in temperature and pressure, i.e.
www.brocku.ca /earthsciences/people/gfinn/petrology/metaintr.htm   (141 words)

  
 Geoscience - The Earth - Shaping the Earth - Metamorphism and metamorphic rocks
Metamorphism is an internal process of the Earth and occurs as a result of changes in temperature and/or pressure.
Contact and dynamic metamorphism are usually restricted to localised areas whereas regional metamorphism affects large areas of the crust, sometimes over tens of thousands of square kilometres.
Retrograde metamorphism is normally produced by repeated regional metamorphism where a lower grade episode is superimposed on a higher grade one.
www.amonline.net.au /geoscience/earth/metamorphism.htm   (2757 words)

  
 Petrogenesis
Heat capable of catalyzing a metamorphic reaction may be supplied by nearby igneous intrusions, the latent heat of crystallization of a nearby solidifying magma, or by the geothermal gradient within the earth's crust.
Thermal metamorphism and dynamic metamorphism are types of isochemical metamorphism, whereas hydrothermal metamorphism typically implies allochemical metamorphism and the introduction of previously absent elements.
Since metamorphism is regulated by kinetic processes, the innermost portion of a mineral sample may contain the original reactant while the outermost layers are of the new composition and are in equilibrium with the surrounding system.
dave.ucsc.edu /myrtreia/petrogene.html   (7748 words)

  
 Multiple choice
During metamorphism the texture of the parent material (the protolith) may change or its mineralogy may change -- new minerals may grow at the expense of the original minerals.
The goal of the geologist is to "see through" the effects of metamorphism and determine the parent rock type.
The greater the pressure and temperature the higher the degree of metamorphism.
www.uh.edu /~jbutler/physical/chapter8notes.html   (804 words)

  
 METAMORPHISM
A variation on regional metamorphism is burial metamorphism, the latter occurs solely in response to burial.
Metamorphic aureole - Zone characterized by a certain mineral or assemblage of minerals which differ from those originally present in the protolith (starting material).
Metamorphic facies - An assemblage of minerals that reached equilibrium under a specific set of temperature and pressure conditions.
geology.csupomona.edu /drjessey/class/Gsc101/Meta.html   (872 words)

  
 metamorphic
Metamorphism occurs when rocks are subjected to high heat and pressure.
Regional metamorphism usually occurs at subduction zones after subduction is finished and causes collision of continental masses.
is the low-temperature, high pressure metamorphism that occurs in the shallower parts of subduction zones.
www-class.unl.edu /geol101i/07_metamorphic.htm   (1423 words)

  
 VERY LOW-GRADE METAMORPHISM in the PREALPES
The burial metamorphism of the Préalpes Médianes by the superposition of the Nappe Supérieure and the Breccia nappe is corroborated by syn-metamorphic internal deformation mechanisms associated with the arrival of the latter nappes (Mosar 1989, 1991).
The increasing degree of metamorphism goes hand in hand with a change in the chemical composition of the white micas which have a tendency to an evolution from a illite type to a muscovite type.
Studying the metamorphism of the units underlying the Préalpes médianes shows that the metamorphism of the Préalpes médianes is transported.
www-sst.unil.ch /research/prealps/METAMO.HTM   (1060 words)

  
 Oxford Brookes - Geology - 8328 Metamorphic Petrology   (Site not responding. Last check: 2007-10-26)
Metamorphism is caused by a variety of processes, ranging from progressive burial and consequently heating of thick sedimentary sequences, through igneous activity and even the impact of meteorites with the earths surface.
Contact or thermal metamorphism is the metamorphism that results from the rise in temperature in the surrounding country rocks near to igneous intrusions.
Hydrothermal metamorphism involves chemical change as an integral part of the process and is the result of the circulation of hot water through a body of rock along fissures and cracks.
www.brookes.ac.uk /geology/8361/1998/freya/met.html   (1542 words)

  
 Geology Class Notes   (Site not responding. Last check: 2007-10-26)
Metamorphism is the solid-state transformation of pre-existing rock into texturally or mineralogically distinct new rock as the result of high temperature high pressure, or both.
Metamorphism may be regional, involving the burial, transformation, and exhumation of entire regions, or contact, where sediments are transformed by contact with an igneous intrusion.
Metamorphism is usually isochemical, meaning that elements are not gained or lost, just the minerals are transformed.
ruby.colorado.edu /~smyth/G101-8.html   (493 words)

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