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Encyclopedia > Serpentinite
A sample of serpentinite rock, partially made up of chrysotile
A sample of serpentinite rock, partially made up of chrysotile

Serpentinite is a rock comprised of one or more serpentine minerals. Minerals in this group are formed by serpentinization, a hydration and metamorphic transformation of ultramafic rock from the Earth's mantle. The alteration is particularly important at the sea floor at tectonic plate boundaries. It is the state rock of California, USA. Image File history File links Mineraly. ... Image File history File links Mineraly. ... Chrysotile Asbestos Chrysotile is an asbestiform sub-group within the serpentine group of minerals. ... The rocky side of a mountain creek near Orosí, Costa Rica. ... Serpentine Serpentine is a group of common rock-forming hydrous magnesium iron phyllosilicate ((Mg, Fe)3Si2O5(OH)4) minerals; it is also often rich in other metal ores, including chromium, manganese, cobalt and nickel. ... Minerals are natural compounds formed through geological processes. ... Quartzite, a form of metamorphic rock, from the Museum of Geology at University of Tartu collection. ... Ultramafic (or ultrabasic) rocks are igneous rocks with very low silica content (less than 45%), generally >18% MgO, high FeO, low potassium and are composed of usually greater than 90% mafic minerals (dark colored, high magnesium and iron content). ... Earth cutaway from core to exosphere. ... Bridge across the Álfagjá rift valley in southwest Iceland, the boundary of the Eurasian and North American continental tectonic plates. ... Official language(s) English Capital Sacramento Largest city Los Angeles Area  Ranked 3rd  - Total 158,302 sq mi (410,000 km²)  - Width 250 miles (400 km)  - Length 770 miles (1,240 km)  - % water 4. ...

Contents

Formation

Serpentinization is a geological low-temperature and metamorphic process involving heat and water in which low-silica mafic and ultramafic rocks are oxidized and hydrolyzed with water into serpentinite. Peridotite, including dunite, at and near the seafloor and in mountain belts is converted to serpentine, brucite, magnetite, and other minerals -- some rare, such as awaruite (Ni3Fe), and even native iron. In the process large amounts of water are absorbed into the rock increasing the volume and destroying the structure. Quartzite, a form of metamorphic rock, from the Museum of Geology at University of Tartu collection. ... The chemical compound silicon dioxide, also known as silica, is the oxide of silicon, chemical formula SiO2. ... In geology, mafic minerals and rocks are silicate minerals, magmas, and volcanic and intrusive igneous rocks that have relatively high concentrations of the heavier elements. ... Ultramafic (or ultrabasic) rocks are igneous rocks with very low silica content (less than 45%), generally >18% MgO, high FeO, low potassium and are composed of usually greater than 90% mafic minerals (dark colored, high magnesium and iron content). ... The most fundamental reactions in chemistry are the redox processes. ... Hydrolysis is a chemical process in which a molecule is cleaved into two parts by the addition of a molecule of water. ... Peridotite Peridotite is a dense, coarse-grained rock, consisting mostly of the minerals olivine and pyroxene. ... Dunite is an igneous, plutonic rock, of ultramafic composition, with coarse grained or phaneritic texture. ... Serpentine Serpentine is a group of common rock-forming hydrous magnesium iron phyllosilicate ((Mg, Fe)3Si2O5(OH)4) minerals; it is also often rich in other metal ores, including chromium, manganese, cobalt and nickel. ... Brucite is the mineral form of magnesium hydroxide, with the chemical formula Mg(OH)2. ... // Headline text Magnetite is a ferrimagnetic mineral form of iron(II,III) oxide, with chemical formula Fe3O4, one of several iron oxides and a member of the spinel group. ... General Name, Symbol, Number iron, Fe, 26 Chemical series transition metals Group, Period, Block 8, 4, d Appearance lustrous metallic with a grayish tinge Atomic mass 55. ...


The density changes from 3.3 to 2.7 g/cm3 with a concurrent volume increase of about 40%. The reaction is exothermic and large amounts of heat energy are produced in the process.


Rock temperatures can be raised by about 260 oC, providing an energy source for formation of non-volcanic hydrothermal vents. The magnetite-forming chemical reactions produce hydrogen gas. Sulfates and carbonates are reduced and form methane and hydrogen sulfide. The hydrogen, methane, and hydrogen sulfide provide energy sources for deep sea chemotroph microorganisms. A hydrothermal vent A hydrothermal vent is a fissure in a planets surface from which geothermally heated water issues. ... This article is about the chemistry of hydrogen. ... In inorganic chemistry, a sulfate (IUPAC-recommended spelling; also sulphate in British English) is a salt of sulfuric acid. ... In organic chemistry, a carbonate is a salt of carbonic acid. ... Methane is the principal component of natural gas. ... Hydrogen sulfide (hydrogen sulphide in British English), H2S, is a colorless, toxic, flammable gas that is responsible for the foul odor of rotten eggs and flatulence. ... Flowchart to determine if a species is autotroph, heterotroph, or a subtype Chemotrophs are organisms that obtain energy by the oxidation of electron donating molecules in their environments. ... A cluster of Escherichia colibacteria magnified 10,000 times. ...


Serpentinite reactions

Serpentinite is formed from olivine via several reactions, some of which are complementary. Olivine is a solid solution between the magnesium-endmember forsterite and the iron-endmember fayalite. Serpentinite reactions 1a and 1b, below, exchange silica between forsterite and fayalite to form serpentine-group minerals and magnetite. These are highly exothermic reactions. Olivine basalt The mineral olivine is a magnesium iron silicate with the formula (Mg,Fe)2SiO4. ... Fig. ... General Name, Symbol, Number magnesium, Mg, 12 Chemical series alkaline earth metals Group, Period, Block 2, 3, s Appearance silvery white Atomic mass 24. ... General Name, Symbol, Number iron, Fe, 26 Chemical series transition metals Group, Period, Block 8, 4, d Appearance lustrous metallic with a grayish tinge Atomic mass 55. ...


Reaction 1a:


Other possibilities include the reaction of olivine plus water to yield serpentine plus Mg(OH)2 (brucite), and reactions in which magnesium and silica are transported out of the serpentinizing volume. Brucite is the mineral form of magnesium hydroxide, with the chemical formula Mg(OH)2. ...


A similar suite of reactions involves pyroxene-group minerals, though less readily and with complication of the additional end-products due to the wider compositions of pyroxene and pyroxene-olivine mixes. Talc and magnesian chlorite are possible products, together with the serpentine minerals antigorite, lizardite, and chrysotile. The final mineralogy depends both on rock and fluid compositions, temperature, and pressure. Antigorite forms in reactions at temperatures that can exceeed 600°C during metamorphism, and it is the serpentine-group mineral stable at the highest temperatures. Lizardite and chrysotile can form at low temperatures very near the Earth's surface. Fluids involved in serpentinite formation commonly are highly reactive and may transport calcium and other elements into surrounding rocks; fluid reaction with these rocks may create metasomatic reaction zones enriched in calcium and called rodingites. Figure 1:Mantle-peridotite xenolith with green peridot olivine and black pyroxene crystals from San Carlos Indian Reservation, Gila Co. ... Talc block Talcum Powder Talc is a mineral composed of hydrated magnesium silicate with the chemical formula H2Mg3(SiO3)4 or Mg3Si4O10(OH)2. ... This discusses some chlorine compounds. ... Antigorite is a monoclinic mineral from the kaolinite-serpentine group. ... Serpentine Serpentine is a group of common rock-forming hydrous magnesium iron phyllosilicate ((Mg,Fe)3Si2O5(OH)4) minerals. ... Chrysotile Asbestos Chrysotile is an asbestiform sub-group within the serpentine group of minerals. ... Serpentine Serpentine is a group of common rock-forming hydrous magnesium iron phyllosilicate ((Mg, Fe)3Si2O5(OH)4) minerals; it is also often rich in other metal ores, including chromium, manganese, cobalt and nickel. ... General Name, Symbol, Number calcium, Ca, 20 Chemical series alkaline earth metals Group, Period, Block 2, 4, s Appearance silvery white Atomic mass 40. ... Metasomatism is a geologic process where metamorphism causes an alteration in a mineral or rock mass that involves a chemical change of the substance with the addition of material, as when chrysolite (olivine) is converted to serpentine basically by the addition of water. ...


In the presence of carbon dioxide, however, serpentinitization may form either magnesite (MgCO3) or generate methane (CH4). It is thought that some hydrocarbon gases may be produced by serpentinite reactions within the oceanic crust, and the serpentinite reaction is a key argument for the theory of abiogenic petroleum origin. The hypothesis of abiogenic petroleum origin holds that most petroleum was formed from deep carbon deposits, perhaps deposits dating to the accretion of the Earth. ...


Reaction 2a:
Olivine + Water + Carbonic acid → Serpentine + Magnetite + Methane



Reaction 2b:
Olivine + Water + Carbonic acid → Serpentine + Magnetite + Magnesite + Silica

Reaction 2a is favored if the serpentinite is Mg-poor or if there isn't enough carbon dioxide to promote talc formation. Reaction 2b is favored in highly magnesian compositions and low partial pressure of carbon dioxide. Talc block Talcum Powder Talc is a mineral composed of hydrated magnesium silicate with the chemical formula H2Mg3(SiO3)4 or Mg3Si4O10(OH)2. ...


The degree to which a mass of ultramafic rock undergoes serpentinisation depends on the starting rock composition and on whether or not fluids transport calcium, magnesium and other elements away during the process. If an olivine composition contains sufficient fayalite, then olivine plus water can completely metamorphose to serpentine and magnetite in a closed system. In most ultramafic rocks formed in the Earth's mantle, however, the olivine is about 90% forsterite endmember, and for that olivine to react completely to serpentine, magnesium must be transported out of the reacting volume. General Name, Symbol, Number calcium, Ca, 20 Chemical series alkaline earth metals Group, Period, Block 2, 4, s Appearance silvery white Atomic mass 40. ... General Name, Symbol, Number magnesium, Mg, 12 Chemical series alkaline earth metals Group, Period, Block 2, 3, s Appearance silvery white Atomic mass 24. ... Earth cutaway from core to exosphere. ...


Serpentinitization of a mass of peridotite usually destroys all previous textural evidence because the serpentine minerals are weak and behave in a very ductile fashion. However, some masses of serpentinite are less severely deformed, as evidenced by the apparent preservation of textures inherited from the peridotite, and the serpentinites may have behaved in a rigid fashion. Rock microstructure includes the texture of a rock and the small scale rock structures. ...


Carbon sequestration

Serpentinite has been proposed as an efficient reagent for carbon sequestration using the magnesite reaction, above, or a variation where serpentine is reacted with carbon dioxde and hydrogen to form magnesite, magnetite, silica. The ideal composition of olivine or serpentinite for this process is thus highly magnesian, to favor production of magnesite and the fixation of carbon. Carbon sequestration from a fossil-fuel power station A carbon dioxide sink or CO2 sink is a carbon reservoir that is increasing in size, and is the opposite of a carbon source. The main sinks are the oceans and growing vegetation. ...


Bleistein or Ofenstein

A lamelled variety of serpentinite is found in South Tyrol and is locally called Bleistein (Leadstone) or Ofenstein (Ovenstone). It was used primarily for building wood burning indoor heating stoves as it has the capacity of storing and dispersing heat very well along the veins. A New York educational documentary film production company [1] is releasing a film that describes the quarrying of this stone and its use in the construction of stoves.


See also

An actively venting calcium carbonate chimney in the Lost City hydrothermal field Lost City is a field of hydrothermal vents in the mid-Atlantic ocean that differ significantly from the black smoker vents found in the late 1970s. ... Olivine basalt The mineral olivine is a magnesium iron silicate with the formula (Mg,Fe)2SiO4. ... Hydrothermal circulation in the oceans is the passage of the water through mid-ocean Ridge (MOR) systems. ... Metasomatism is a geologic process where metamorphism causes an alteration in a mineral or rock mass that involves a chemical change of the substance with the addition of material, as when chrysolite (olivine) is converted to serpentine basically by the addition of water. ... Metamorphism can be defined as the mineralogical, chemical and crystallographic changes in a solid-state rock, i. ... There is also a community named Actinolite,_Ontario in Canada. ... Carbon sequestration from a fossil-fuel power station A carbon dioxide sink or CO2 sink is a carbon reservoir that is increasing in size, and is the opposite of a carbon source. The main sinks are the oceans and growing vegetation. ... Talc carbonate is a geologic term for a suite of rock and mineral compositions found in metamorphic ultramafic rocks. ... The lid of a soapstone box to show the characteristic look of the stone. ... The infamous Face on Mars released on July 25, 1976. ...

External links

  • ZECA Corporation serpentinite carbon sequestration process

References


  Results from FactBites:
 
Serpentinite (297 words)
This 1-1/2 meter serpentinite boulder sits in a place of honor in the roof garden of the Oakland Museum of California, its polished surface gleaming blue and jade-green.
Serpentinite can contain chrysotile, the serpentine mineral that crystallizes in long, thin fibers.
This is the mineral commonly known as asbestos.
  More results at FactBites »

 
 

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