Metasomatism is the chemical alteration of a rock by hydrothermal and other fluids. In Geology, rock is a naturally occurring aggregate of Minerals and/or Mineraloids The Earth's outer solid layer the ‘ Lithosphere Hydrothermal circulation in its most general sense is the circulation of hot water 'hydros' in the Greek meaning water and 'thermos' meaning heat It is also known as "alteration".

Metasomatism can occur via the action of hydrothermal fluids from an igneous or metamorphic source. Igneous rocks (etymology from Latin ignis, fire are rocks formed by solidification of cooled Magma (molten rock 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

In the igneous environment, metasomatism creates skarns, greisen, and may affect hornfels in the contact metamorphic aureole adjacent to an intrusive rock mass. Igneous rocks (etymology from Latin ignis, fire are rocks formed by solidification of cooled Magma (molten rock Skarn is a Metamorphic rock that is usually variably colored green or red occasionally grey black brown or white Greisen is a highly altered granitic rock or Pegmatite. Greisen is formed by autogenic alteration of a granite and is a class of endoskarn. Hornfels ( German, meaning "hornstone" is the group designation for a series of contact metamorphic rocks that have been baked and indurated by the heat In Geology, an intrusion is a body of Igneous rock that has Crystallized from molten Magma below the surface of the Earth.

Metasomatic albite + hornblende + tourmaline alteration of metamorphosed granite, Stone Mountain, Atlanta

In the metamorphic environment, metasomatism is created by mass transfer from a volume of metamorphic rock at higher stress and temperature into a zone with lower stress and temperature, with metamorphic hydrothermal solutions acting as a solvent. Albite is a plagioclase Feldspar Mineral. It is the sodium endmember of the Plagioclase Solid solution series 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 Tourmaline is a Crystal Silicate mineral compounded with elements such as Aluminium, Iron, Magnesium, Sodium, Lithium Granite (ˈɡrænɪt is a common and widely occurring type of intrusive, Felsic, igneous rock. This article is about Stone Mountain in Georgia USA For other uses see Stone Mountain (disambiguation. Metamorphic rock is the result of the transformation of an existing rock type the protolith, in a process called Metamorphism, which means "change Stress is a measure of the average amount of Force exerted per unit Area. 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 A solvent is a liquid or gas that dissolves a solid liquid or gaseous Solute, resulting in a Solution. This can be envisaged as the metamorphic rocks within the deep crust losing fluids and dissolved mineral components as hydrous minerals break down, with this fluid percolating up into the shallow levels of the crust to chemically change and alter these rocks. In Geology, a crust is the outermost solid shell of a planet or moon A mineral is a naturally occurring substance formed through geological processes that has a characteristic chemical composition a highly ordered atomic structure and specific

This mechanism implies that metasomatism is open system behaviour, which is different from classical metamorphism which is the in-situ mineralogical change of a rock without appreciable change in the chemistry of the rock. 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 Because metamorphism usually requires water in order to facilitate metamorphic reactions, metasomatism and metamorphism nearly always occur together. Water is a common Chemical substance that is essential for the survival of all known forms of Life.

Further, because metasomatism is a mass transfer process, it is not restricted to the rocks which are changed by addition of chemical elements and minerals or hydrous compounds. In all cases, to produce a metasomatic rock some other rock is also metasomatised, if only by dehydration reactions with minimal chemical change. This is best illustrated by gold ore deposits which are the product of focused concentration of fluids derived from many cubic kilometres of dehydrated crust into thin, often highly metasomatised and altered shear zones and lodes. The various theories of ore genesis explain how the various types of mineral deposits form within the Earth's crust. CM3 redirects here If you were looking for the 3rd game in the Cooking Mama series abbreviated as CM3 see here. In Geology, a crust is the outermost solid shell of a planet or moon Study of geological shear is related to the study of Structural geology, Rock microstructure or rock texture and fault mechanics. In Geology a lode is the metalliferous Ore that fills a Fissure in a rock or a vein of ore deposited between layers of The source region is often largely chemically unaffected compared to the highly hydrated, altered shear zones, but both must have undergone complementary metasomatism.

Metasomatism is more complicated in the Earth's mantle, because the composition of peridotite at high temperatures can be changed by infiltration of carbonate and silicate melts and by carbon dioxide-rich and water-rich fluids, as discussed by Luth (2003). The mantle is a part of an Astronomical object. The interior of the Earth, similar to the other Terrestrial planets, is Chemically divided A peridotite is a dense coarse-grained Igneous rock, consisting mostly of the minerals Olivine and Pyroxene. In Chemistry, a carbonate is a salt or Ester of Carbonic acid. For the Artificial intelligence Androids of the 1990s Science fiction series Space Above and Beyond, see Silicate (AI Carbon dioxide ( Chemical formula:) is a Chemical compound composed of two Oxygen Atoms covalently bonded to a single Metasomatism is thought to be particularly important in changing the composition of mantle peridotite below island arcs as water is driven out of ocean lithosphere during subduction. A volcanic arc is a chain of volcanic islands or Mountains formed by Plate tectonics as an oceanic Tectonic plate subducts under An ocean (from Greek, ''Okeanos'' (Oceanus) is a major body of saline water, and a principal component of the Hydrosphere. The lithosphere (IPA, from the Greek λίθος for "rocky" + σφαίρα for "sphere" is the solid outermost shell of a rocky Planet. 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 Metasomatism has also been considered critical for enriching source regions of some silica-undersaturated magmas. Normative mineralogy is a geochemical calculation of the whole rock geochemistry of a rock sample which estimates the idealised mineralogy of a rock according to the principles Magma (Plurals magmas and magmata) is molten rock that sometimes forms beneath the surface of the Earth (or any other Terrestrial planet Carbonatite melts are often considered to have been responsible for enrichment of mantle peridotite in incompatible elements. Carbonatites (kɑrˈbɒnətaɪt are Intrusive or extrusive Igneous rocks defined by mineralogy that comprises more than 50 volume-% Carbonate Incompatible element is a term used in Petrology and Geochemistry.

Types of metasomatites

Metasomatic rocks can be extremely varied. Often, metasomatised rocks are pervasively but weakly altered, such that the only evidence of alteration is bleaching, change in colour or change in the crystallinity of micaceous minerals.

In such cases, characterising alteration often requires microscope investigation of the mineral assemblage of the rocks to characterise the minerals, any additional mineral growth, changes in protolith minerals, and so on.

In some cases, geochemical evidence can be found of metasomatic alteration processes. This is usually in the form of mobile, soluble elements such as barium, strontium, rubidium, calcium and some rare earth elements. Barium (ˈbɛəriəm is a Chemical element. It has the symbol Ba, and Atomic number 56 Strontium (ˈstrɒntiəm /ˈstrɒnʃiəm/) is a Chemical element with the symbol Sr and the Atomic number 38 Rubidium (ruːˈbɪdiəm /rəˈbɪdiəm/ is a Chemical element with the symbol Rb and Atomic number 37 Calcium (ˈkælsiəm is the Chemical element with the symbol Ca and Atomic number 20 Rare earth elements and rare earth metals are according to IUPAC, the collection of seventeen Chemical elements in the Periodic table, namely However, to characterise the alteration properly, it is necessary to compare altered with unaltered samples.

When the process becomes extremely advanced, typical metasomatites can include:

• Chlorite or mica whole-rock replacement in shear zones, resulting in rocks in which the existing mineralogy has been completely recrystallised and replaced by hydrated minerals such as chlorite, muscovite, and serpentine. The chlorites are a group of phyllosilicate Minerals Chlorites can be described by the following four endmembers based on their chemistry via substitution The word "mica" is thought to be derived from the Latin word la micare, "glitteren" in reference to the brilliant appearance of this mineral (especially Muscovite (also known as Common Mica, Isinglass, or Potash mica) is a phyllosilicate Mineral of Aluminium The serpentine group describes a group of common rock-forming hydrous Magnesium Iron phyllosilicate (()3 Minerals they
• Skarn and skarnoid rock types, typically adjacent to granite intrusions and adjacent to reactive lithologies such as limestone, marl and banded iron formation. Skarn is a Metamorphic rock that is usually variably colored green or red occasionally grey black brown or white Granite (ˈɡrænɪt is a common and widely occurring type of intrusive, Felsic, igneous rock. Limestone is a Sedimentary rock composed largely of the Mineral Calcite ( Calcium carbonate: CaCO3 Marl or Marlstone is a Calcium carbonate or lime -rich mud or Mudstone which contains variable amounts of Clays and Aragonite Banded iron formations (also known as banded ironstone formations or BIF s are a distinctive type of rock often found in primordial ( Precambrian) Sedimentary
• Greisen deposits within granite margins and cupolas. Greisen is a highly altered granitic rock or Pegmatite. Greisen is formed by autogenic alteration of a granite and is a class of endoskarn. Granite (ˈɡrænɪt is a common and widely occurring type of intrusive, Felsic, igneous rock.

Effects of metasomatism in mantle peridotite can be either modal or cryptic. In cryptic metasomatism, mineral compositions are changed, or introduced elements are concentrated on grain boundaries and the peridotite mineralogy appears unchanged. In modal metasomatism, new minerals are formed.

Cryptic metasomatism may be caused as rising or percolating melts interact with surrounding peridotite, and compositions of both melts and peridotite are changed. At high mantle temperatures, solid-state diffusion can also be effective in changing rock compositions over tens of centimeters adjacent to melt conduits: gradients in mineral composition adjacent to pyroxenite dikes may preserve evidence of the process. Diffusion is the net movement of particles (typically molecules from an area of high concentration to an area of low concentration by uncoordinated random movement A centimetre ( American spelling: centimeter, symbol cm) is a unit of Length in the Metric system, equal to one hundredth Pyroxenite is an Ultramafic Igneous rock consisting essentially of Minerals of the Pyroxene group such as Augite and

Modal metasomatism may result in formation of amphibole and phlogopite, and the presence of these minerals in peridotite xenoliths has been considered strong evidence of metasomatic processes in the mantle. Amphibole (pronounced amfi-bowl defines an important group of generally dark-colored rock-forming inosilicate Minerals composed of double chain SiO4 Phlogopite is a yellow greenish or reddish-brown member of the Mica family of phyllosilicates. This article concerns the geologic term for other uses see Xenolith (disambiguation A xenolith ( Greek: 'foreign rock' is a rock Formation of minerals less common in peridotite, such as dolomite, calcite, ilmenite, rutile, and armalcolite, is also attributed to melt or fluid metasomatism. Dolomite (ˈdɒləmaɪt is the name of a Sedimentary Carbonate rock and a Mineral, both composed Calcite is a carbonate mineral and the most stable polymorph of Calcium carbonate ( Ca[[carbon C]] O 3 Ilmenite is a weakly magnetic titanium-iron oxide Mineral which is iron-black or steel-gray Rutile is a Mineral composed primarily of Titanium dioxide, Ti[[oxygen O]]2 Armalcolite is a Mineral that was discovered at Tranquility Base on the Moon by the Apollo 11 crew in 1969

Alteration assemblages

Investigation of altered rocks in hydrothermal ore deposits has highlghted several ubiquitous types of alteration assemblages which create distinct groups of metasomatic alteration effects, textures and mineral assemblages.

• Propylitic Alteration is caused by iron and sulfur-bearing hydrothermal fluids, and typically results in epidote-chlorite-pyrite alteration, often with hematite and magnetite facies
• Albite-epidote alteration is caused by silica-bearing fluids rich in sodium and calcium, and typically results in weak albite-silica-epidote
• Potassic Alteration, typical of lode gold deposits, results in production of micaceous, potassic minerals such as biotite in iron-rich rocks, muscovite mica or sericite in felsic rocks, and orthoclase (adularia) alteration, often quite pervasive and producing distinct salmon-pink alteration vein selvages. Iron (ˈаɪɚn is a Chemical element with the symbol Fe (ferrum and Atomic number 26 Sulfur or sulphur (ˈsʌlfɚ see spelling below) is the Chemical element that has the Atomic number 16 Epidote is a Calcium Aluminium Iron sorosilicate Mineral, Ca2Al2(Fe3+Al(SiO4(Si2O7O(OH Hematite, also spelt hæmatite, is the Mineral form of Iron(III oxide (Fe2O3 one of several Iron oxides Magnetite is not to be confused with Magnesite or Maghemite. Magnetite is a ferrimagnetic Mineral with chemical Epidote is a Calcium Aluminium Iron sorosilicate Mineral, Ca2Al2(Fe3+Al(SiO4(Si2O7O(OH The Chemical compound silicon dioxide, also known as silica or silox (from the Latin " Silex " is an Oxide Sodium (ˈsoʊdiəm is an element which has the symbol Na( Latin natrium, from Arabic natrun) atomic number 11 atomic mass 22 Calcium (ˈkælsiəm is the Chemical element with the symbol Ca and Atomic number 20 Albite is a plagioclase Feldspar Mineral. It is the sodium endmember of the Plagioclase Solid solution series The Chemical compound silicon dioxide, also known as silica or silox (from the Latin " Silex " is an Oxide Epidote is a Calcium Aluminium Iron sorosilicate Mineral, Ca2Al2(Fe3+Al(SiO4(Si2O7O(OH Potassium (pəˈtæsiəm is a Chemical element. It has the symbol K (kalium from qalīy Atomic number 19 and Atomic mass 39 Biotite is a common phyllosilicate Mineral within the Mica group with the approximate chemical formula K(Mg Fe3AlSi3O10(F Sericite is a fine grained Mica, either Muscovite, Illite, or Paragonite. Physical properties Orthoclase crystallizes in the Monoclinic crystal system

Rarer types of hydrothermal fluids may include highly carbonic fluids, resulting in advanced carbonation reactions of the host rock typical of calc-silicates, and silica-hematite fluids resulting in production of jasperoids, manto ore deposits and pervasive zones of silicification, typically in dolomite formations. Jasperoid is a rare peculiar type of metasomatic alteration and occurs in two main forms sulfidic jasperoids and hematitic jasperoids Manto orebodies are stratabound irregular to rod shaped Ore occurrences usually horizontal or near horizontal in attitude Dolomite (ˈdɒləmaɪt is the name of a Sedimentary Carbonate rock and a Mineral, both composed

References

• Luth, R. W. , Mantle volatiles -- distribution and consequences. In The Mantle and Core (ed. R. W. Carlson) Volume 2 Treatise on Geochemistry (editors H. D. Holland and K. K. Turekian), Elsevier-Pergamon, Oxford, pages 319-361 (2003). ISBN 0-08-043751-6

See also

• Hydrothermal
• Ore genesis
• Greisen
• Skarn
• Hornfels