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The metamorphic facies are groups of mineral compositions in metamorphic rocks, that are typical for a certain field in pressure-temperature space. A mineral is a naturally occurring substance formed through geological processes that has a characteristic chemical composition a highly ordered atomic structure and specific Metamorphic rock is the result of the transformation of an existing rock type the protolith, in a process called Metamorphism, which means "change Pressure (symbol 'p' is the force per unit Area applied to an object in a direction perpendicular to the surface Temperature is a physical property of a system that underlies the common notions of hot and cold something that is hotter generally has the greater temperature Rocks which contain certain minerals can therefore be linked to certain tectonic settings. This article discusses the geologic usage for the philosophical or architectural usage see Architectonics ' Or see Plate tectonics.

Contents

Definition

The name facies was first used for specific sedimentary environments in sedimentary rocks by Swiss geologist Amanz Gressly in 1838. Sedimentary rock is one of the three main rock types (the others being igneous and Metamorphic rock) Switzerland (English pronunciation; Schweiz Swiss German: Schwyz or Schwiiz Suisse Svizzera Svizra officially the Swiss Confederation ( July 17, 1814 - April 13, 1865) was a was a Swiss geologist and paleontologist. Analogous with these sedimentary facies a number of metamorphic facies were proposed in 1921 by Finnish petrologist Pentti Eelis Eskola. Finland, officially the Republic of Finland ( is a Nordic country situated in the Fennoscandian region of northern Europe. Pentti Eelis Eskola (1883–1964 was a Finnish Geologist who developed the concept of metamorphic Facies. Eskola's classification was refined in the 70's by New-Zealand geologist Francis John Turner.

Underlying principles

The different metamorphic facies are defined by the mineralogical composition of a rock. When the temperature or pressure in a rock body change, the rock can cross into a different facies and some minerals become stable while others become unstable or metastable. A stable is a Building in which Livestock, especially Horses are kept Metastability is a general scientific concept which describes states of delicate equilibrium Whether minerals really react depends on the reaction kinetics, the activation energy of the reaction and how much fluid is present in the rock. Chemical kinetics, also known as reaction kinetics is the study of rates of chemical processes In Chemistry, activation energy, also called midnight energy, is a term introduced in 1889 by the Swedish scientist Svante Arrhenius, that is defined FLUID ( F ast L ight '''U'''ser '''I'''nterface D esigner is a graphical editor that is used to produce FLTK Source code

The minerals in a metamorphic rock and their age relations can be studied by optical microscopy or Scanning Electron Microscopy of thin sections of the rock. The optical microscope, often referred to as the "light microscope" is a type of Microscope which uses Visible light and a system of lenses to The scanning electron microscope ( SEM) is a type of Electron microscope that images the sample surface by scanning it with a high-energy beam of Electrons In Optical mineralogy and Petrography, a thin section is a Laboratory preparation of a rock, Mineral or Soil sample for Apart from the metamorphic facies of a rock, a whole terrane can be described by the abbrevations LT, MT, HT, LP, MP, HP (from low, medium or high; pressure or temperature). A terrane in Geology is a fragment of crustal material formed on or broken off from one Tectonic plate and accreted — " sutured " Since the 80's the term UHP (ultra high pressure) is used for rocks that saw extreme pressures.

Which minerals grow in a rock is also dependent of the original composition of the protolith (the original rock before metamorphosis). Protolith refers to the precursor Lithology of a Metamorphic rock Carbonate rocks have a different composition from say a basalt lava, the minerals that can grow in them are different too. In Chemistry, a carbonate is a salt or Ester of Carbonic acid. Basalt (bəˈsɔːlt ˈbeisɔːlt ˈbæsɔːlt is a common Extrusive Volcanic rock. Lava is molten rock expelled by a Volcano during an eruption When first expelled from a volcanic vent it is a Liquid at Temperatures Therefore a metapsammite and a metapelite will have different mineralogical compositions even though they were in the same metamorphic facies. This article is about a type of sedimentary rock For the work by Archimedes, Psammites see The Sand Reckoner. Pelite ( Greek Pelos, Clay is a descriptive name for a Clastic rock with a grain size of less than 1/16mm (originally sand or silt Examples include

Index minerals

Main article: index mineral

Every metamorphic facies has some index minerals by which it can by recognized. An index mineral is used in geology to determine the degree of Metamorphism a rock has experienced That does not mean these minerals will necessarily be visible with the naked eye, or even exist in the rock; when the rock did not have the right chemical composition they will not grow.

Very typical index minerals are the polymorphs of alumino-silicate (Al2SiO5, all are nesosilicates). The silicate minerals make up the largest and most important class of rock-forming Minerals They are classified based on the structure of their silicate Ion group Andalusite is stable at low pressure, kyanite is stable at high pressure but relatively low temperature and sillimanite is stable at high temperature. Andalusite is an Aluminium nesosilicate Mineral with the chemical formula Al2SiO5 Kyanite, whose name derives from the Greek word kyanos, meaning blue is a typically blue Silicate Mineral, commonly found in Aluminium -rich Sillimanite also called Bucholzite is an alumino-silicate Mineral with the Chemical formula Al2SiO5

Metamorphic facies and their mineral assemblages

Zeolite facies (LP/LT)

Main article: zeolite facies

The zeolite facies is the metamorphic facies with the lowest metamorphic grade. Zeolite facies describes the mineral assemblage resulting from the pressure and temperature conditions of low-grade Metamorphism. At lower temperature and pressure processes in the rock are called diagenesis. In Geology and Oceanography, diagenesis is any chemical physical or biological change undergone by a Sediment after its initial deposition and during The facies is named for zeolites, strongly hydrated tectosilicates. Zeolites (Greek zein, "to boil" lithos, "a stone" are hydrated Aluminosilicate Minerals and have a micro-porous structure The silicate minerals make up the largest and most important class of rock-forming Minerals They are classified based on the structure of their silicate Ion group It can have the following mineral assemblages:

In meta-igneous rocks and greywackes:

In metapelites:

Prehnite-pumpellyite-facies (LP/LT)

Main article: prehnite-pumpellyite facies

The prehnite-pumpellyite facies is a little higher in pressure and temperature than the zeolite facies. Greywacke ( German grauwacke, signifying a grey earthy rock is a variety of Sandstone generally characterized by its hardness dark color and poorly-sorted Heulandite is the name of a series of tecto-silicate Minerals of the Zeolite group Analcime or analcite (from the Greek analkimos - "weak" is a white grey or colourless tectosilicate Mineral. Quartz (from German) is the most abundant Mineral in the Earth 's Continental crust (although Feldspar is more common in Clay minerals are hydrous Aluminium phyllosilicates, sometimes with variable amounts of Iron, Magnesium, Alkali metals Alkaline Laumontite is a Mineral, one of the Zeolite group Its molecular formula is (2 · 4 H2O, a hydrated calcium-aluminium Albite is a plagioclase Feldspar Mineral. It is the sodium endmember of the Plagioclase Solid solution series This discusses some chlorine compounds Chlorite is also a type of mineral see Chlorite group. Pelite ( Greek Pelos, Clay is a descriptive name for a Clastic rock with a grain size of less than 1/16mm (originally sand or silt Examples include Muscovite (also known as Common Mica, Isinglass, or Potash mica) is a phyllosilicate Mineral of Aluminium The prehnite-pumpellyite facies is a metamorphic facies typical of subseafloor alteration of the Oceanic crust around Mid-ocean ridge spreading centres It is named for the minerals prehnite (a Ca-Al-phyllosilicate) and pumpellyite (a sorosilicate). Prehnite is a phyllosilicate of Calcium and Aluminium with the formula Ca2Al(AlSi3O10(OH2 Calcium (ˈkælsiəm is the Chemical element with the symbol Ca and Atomic number 20 WikipediaNaming The silicate minerals make up the largest and most important class of rock-forming Minerals They are classified based on the structure of their silicate Ion group Pumpellyite is a sorosilicate mineral rather a group of closely related minerals or Solid solution series pumpellyite-(Mg Ca2MgAl2(SiO4(Si2O7(OH2·(H2O For the Artificial intelligence Androids of the 1990s Science fiction series Space Above and Beyond, see Silicate (AI The prehnite-pumpellyite is characterized by the mineral assemblages:

In meta-igneous rocks and greywackes:

In metapelites:

Greenschist facies (MP/MT)

Main article: greenschist facies

The greenschist facies is at medium pressure and temperature. Prehnite is a phyllosilicate of Calcium and Aluminium with the formula Ca2Al(AlSi3O10(OH2 Pumpellyite is a sorosilicate mineral rather a group of closely related minerals or Solid solution series pumpellyite-(Mg Ca2MgAl2(SiO4(Si2O7(OH2·(H2O Epidote is a Calcium Aluminium Iron sorosilicate Mineral, Ca2Al2(Fe3+Al(SiO4(Si2O7O(OH Greenschist - also known as greenstone - is a general field petrologic term applied to metamorphic and/or altered Mafic Volcanic rock The facies is named for the typical schistose texture of the rocks and green colour of the minerals chlorite, epidote and actinolite. The schists form a group of medium-grade Metamorphic rocks chiefly notable for the preponderance of lamellar Minerals such as Micas chlorite Texture refers to the properties held and sensations caused by the external surface of objects received through the sense of touch. The chlorites are a group of phyllosilicate Minerals Chlorites can be described by the following four endmembers based on their chemistry via substitution Epidote is a Calcium Aluminium Iron sorosilicate Mineral, Ca2Al2(Fe3+Al(SiO4(Si2O7O(OH For the community in Canada see Actinolite Ontario. For the Sailor Moon character Characteristic mineral assemblages are:

In metabasites:

In metagreywackes:

In metapelites:

In Si-rich dolostones:

Amphibolite-facies (MP/MT-HT)

Main article: amphibolite facies

The amphibolite facies is a facies of medium pressure and average to high temperature. For the community in Canada see Actinolite Ontario. For the Sailor Moon character Chloritoid is a silicate mineral of metamorphic origin It is an Iron Magnesium Manganese Paragonite, also known as Natron-Glimmer, Paragonit or Paragonita, is a Mineral, related to Muscovite. Biotite is a common phyllosilicate Mineral within the Mica group with the approximate chemical formula K(Mg Fe3AlSi3O10(F Manganese (ˈmæŋgəniːz is a Chemical element, designated by the symbol Mn. The garnet group includes a group of minerals that have been used since the Bronze Age as gemstones and abrasives Spessartine previously named spessartite, is a Nesosilicate, Manganese Aluminium Garnet, Mn 3 Al 2( Silicon (ˈsɪlɪkən or /ˈsɪlɪkɒn/ silicium is the Chemical element that has the symbol Si and Atomic number 14 Dolostone is a sedimentary Carbonate rock that contains a high percentage of the Mineral Dolomite. Dolomite (ˈdɒləmaɪt is the name of a Sedimentary Carbonate rock and a Mineral, both composed It is called after amphiboles that form under such circumstances. Amphibole (pronounced amfi-bowl defines an important group of generally dark-colored rock-forming inosilicate Minerals composed of double chain SiO4 It has the following mineral assemblages:

In metabasites:

In metapelites:

In Si-dolostones:

Granulite facies (MP/HT)

Main article: granulite facies

The granulite facies is the highest grade of metamorphism at medium pressure. Hornblende is a complex inosilicate series of Minerals Hornblende is not a recognized mineral in its own right but the name is used as a general or field term to Plagioclase is a very important series of tectosilicate Minerals within the Feldspar family The garnet group includes a group of minerals that have been used since the Bronze Age as gemstones and abrasives Cummingtonite or magnesium iron silicate hydroxide is a metamorphic Amphibole with the Chemical composition ( Mg, Fe)7 Diopside is a Monoclinic Pyroxene Mineral with composition MgCaSi2O6 Staurolite is a red brown to black mostly opaque nesosilicate Mineral with a white streak Kyanite, whose name derives from the Greek word kyanos, meaning blue is a typically blue Silicate Mineral, commonly found in Aluminium -rich Sillimanite also called Bucholzite is an alumino-silicate Mineral with the Chemical formula Al2SiO5 Calcite is a carbonate mineral and the most stable polymorph of Calcium carbonate ( Ca[[carbon C]] O 3 Tremolite is a member of the Amphibole group of Silicate minerals with composition Ca 2 Mg 5 Si 8 Talc (derived from the Persian via Arabic talq) is a Mineral composed of Hydrated Magnesium Silicate with Forsterite (Mg2SiO4 is the magnesium rich end-member of the Olivine Solid solution series Granulites are fine to medium–grained Metamorphic rocks that have experienced high Temperatures of metamorphism composed mainly of Feldspars sometimes associated The depth at which it occurs is not constant. A characteristic mineral for this facies and the pyroxene-hornblende facies is orthopyroxene. The pyroxenes are a group of important rock-forming Silicate minerals found in many Igneous and metamorphic rocks. The granulite facies is characterized by the following mineral assemblages:

In metabasites:

In metapelites:

Blueschist facies (MP-HP/LT)

Main article: blueschist facies

The blueschist facies is at relatively low temperature but high pressure, such as occurs in rocks in a subduction zone. The pyroxenes are a group of important rock-forming Silicate minerals found in many Igneous and metamorphic rocks. The pyroxenes are a group of important rock-forming Silicate minerals found in many Igneous and metamorphic rocks. Cordierite ( Mineralogy) or iolite ( Gemology) is a Magnesium Iron Aluminium cyclosilicate. Physical properties Orthoclase crystallizes in the Monoclinic crystal system Sapphirine is a rare Mineral, a Silicate of Magnesium and Aluminium with the Chemical formula ( Mg, Al)8(Al Osumilite a very rare Hydrate potassium-sodium-iron-magnesium-aluminum Silicate mineral. Blueschist (ˈbluːʃɪst is a rock that forms by the Metamorphism of Basalt and rocks with similar composition at high Pressures and low In Geology, a subduction zone is an area on Earth where two tectonic plates meet and move towards one another with one sliding underneath the other The facies is named after the schistose character of the rocks and the blue minerals glaucophane and lawsonite. Glaucophane is a Mineral belonging to the Amphibole group chemical formula Na 2( Mg, Fe)3 Al 2 Lawsonite is a hydrous calcium aluminium sorosilicate mineral with formula CaAl2Si2O7(OH2·H2O The blueschist facies forms the following mineral assemblages:

In metabasites:

In metagreywackes:

In metapelites:

In carbonate-rocks (marbles):

Eclogite facies (HP/HT)

Main article: eclogite facies

The eclogite facies is the facies at the highest pressure and high temperature. Glaucophane is a Mineral belonging to the Amphibole group chemical formula Na 2( Mg, Fe)3 Al 2 Lawsonite is a hydrous calcium aluminium sorosilicate mineral with formula CaAl2Si2O7(OH2·H2O This discusses some chlorine compounds Chlorite is also a type of mineral see Chlorite group. Titanite or sphene is a Calcium Titanium nesosilicate Mineral, Ca[[titanium Ti]] Si[[oxygen O]]5 Epidote is a Calcium Aluminium Iron sorosilicate Mineral, Ca2Al2(Fe3+Al(SiO4(Si2O7O(OH Phengite is a series name for dioctahedral Micas of composition K(AlMg2(OH2(SiAl4O10 similar to Muscovite but with addition Omphacite is a member of the Pyroxene group of Silicate minerals with formula ( Ca, Na)( Mg, Fe 2+ Al Jadeite is a Pyroxene mineral with composition Na[[aluminum Al]] Si 2 O 6 Aragonite is a Carbonate mineral, one of the two common naturally occurring polymorphs of Calcium carbonate, Ca[[carbon C]] O 3 It is named for the metabasic rock eclogite. Eclogite (ˈɛklədʒaɪt is a coarse-grained Mafic ( Basaltic in composition Metamorphic rock. The eclogite facies had the mineral assemblages:

In metabasites:

In metagranodiorite:

In metapelites:

Albite-epidote-hornfels facies (LP/LT-MT)

The albite-epidote-hornfels facies is a facies at low pressure and relatively low temperatures. This article is about the mineral named zoisite For the Sailor Moon character see Shitennou. It is named for the two minerals albite and epidote, though they are stable in more facies. Albite is a plagioclase Feldspar Mineral. It is the sodium endmember of the Plagioclase Solid solution series Epidote is a Calcium Aluminium Iron sorosilicate Mineral, Ca2Al2(Fe3+Al(SiO4(Si2O7O(OH Hornfels is a rock formed in contact metamorphism, a process that characteristically involves high temperatures but low pressures/depths. Hornfels ( German, meaning "hornstone" is the group designation for a series of contact metamorphic rocks that have been baked and indurated by the heat Metamorphism can be defined as the solid state recrystallisation of pre-existing rocks due to changes in heat and/or pressure and/or introduction of fluids i This facies is characterized by the following minerals:

In metabasites:

In metapelites:

Hornblende-hornfels facies (LP/MT)

The hornblende-hornfels facies is a facies with the same low pressures but slightly higher temperatures as the albite-epidote facies. Though it is named for the mineral hornblende, the appearance of that mineral is not constrained to this facies. The hornblende-hornfels facies has the following mineral assemblages:

In metabasites:

In metapelites:

In K2O-poor sediments or meta-igneous rocks:

In Si-rich dolostones:

Pyroxene-hornfels facies (LP/MT-HT)

The pyroxene-hornfels facies is the contact-metamorphic facies with the highest temperatures and is, like the granulite facies, characterized by the mineral orthopyroxene. Anthophyllite is an Amphibole Mineral: (Mg Fe7Si8O22(OH2 Magnesium Iron inosilicate Andalusite is an Aluminium nesosilicate Mineral with the chemical formula Al2SiO5 It is characterized by the following mineral assemblages:

In metabasites:

In metapelites:

In carbonate rocks:

Sanidinite facies (LP/HT)

The sanidinite facies is a rare facies of extremely high temperatures and low pressure. The Mineral olivine (when gem-quality also called Peridot) is a Magnesium Iron silicate with the formula ( Mg Physical properties Orthoclase crystallizes in the Monoclinic crystal system The spinels are any of a class of Minerals of general formulation XY2 O 4 which Crystallize in the cubic (isometric Periclase occurs naturally in contact Metamorphic rocks and is a major component of most basic Refractory bricks Grossular, also incorrectly called grossularite, is a Calcium - Aluminium mineral species of the Garnet group with the Formula Vesuvianite, also known as idocrase is a green brown yellow or blue silicate mineral. It can only be reached under certain contact-metamorphic circumstances. Due to the high temperature the rock experiences partial melting and glass is formed. This facies is named for the mineral sanidine. Sanidine is the high temperature form of potassium Feldspar (KNa(SiAl4O8 It is characterized by the following mineral assemblages:

In metapelites:

In carbonates:

References

See also

Metamorphic rock is the result of the transformation of an existing rock type the protolith, in a process called Metamorphism, which means "change Metamorphosis is a Biological process by which an Animal physically develops after Birth or hatching involving a conspicuous and relatively
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