Jump to content

Serpentinite: Difference between revisions

From Wikipedia, the free encyclopedia
Browse history interactively
← Previous editNext edit →
Content deleted Content added
VisualWikitext
Citation bot (talk | contribs)
Bots
5,408,772 edits
Removed proxy/dead URL that duplicated identifier. Removed access-date with no URL. | Use this bot. Report bugs. | Suggested by AManWithNoPlan | #UCB_CommandLine
Removed content that related to serpentinization and moved it to a newly formed page named serpentinization. Also added references and fixed hanging statements.
Line 1: Line 1:

{{short description|Rock formed by hydration and metamorphic transformation of olivine}}
{{short description|Rock formed by hydration and metamorphic transformation of olivine}}
{{Use dmy dates|date=May 2022}}
{{Use dmy dates|date=May 2022}}
[[File:Mineraly.sk - chryzotil.jpg|right|thumb|Serpentinite partially made of [[chrysotile]], from Slovakia]]
[[File:Serpentinite sur gneiss.jpg|right|thumb|Serpentinite from the [[Maurienne valley]], Savoie, French Alps]]
[[File:Serpentinite sur gneiss.jpg|right|thumb|Serpentinite from the [[Maurienne valley]], Savoie, French Alps]]
[[File:Serpentinite.JPG|right|thumb|Sample of serpentinite from the [[Golden Gate National Recreation Area]], California, United States]]
[[File:Serpentinite.JPG|right|thumb|Sample of serpentinite from the [[Golden Gate National Recreation Area]], California, United States]]
[[File:Chromitic serpentinite Styria Province, Austria.jpg|thumb|[[Chromite|Chromitic]] serpentinite ({{convert|7.9|cm|abbr=on}} across), [[Styria]] Province, Austria. [[Protolith]] was a Proterozoic-Early Paleozoic [[upper mantle (Earth)|upper mantle]] [[dunite]] [[peridotite]] that has been multiply metamorphosed during the Devonian, Permian, and Mesozoic.]]
[[File:Chromitic serpentinite Styria Province, Austria.jpg|thumb|[[Chromite|Chromitic]] serpentinite ({{convert|7.9|cm|abbr=on}} across), [[Styria]] Province, Austria. [[Protolith]] was a Proterozoic-Early Paleozoic [[upper mantle (Earth)|upper mantle]] [[dunite]] [[peridotite]] that has been multiply metamorphosed during the Devonian, Permian, and Mesozoic.]]
[[File:Folded serpentinite.jpg|thumb|Tightly folded serpentinite from the [[Tux Alps]], Austria. Closeup view about {{convert|30|×|20|cm|abbr=on}}.]]
[[File:Folded serpentinite.jpg|thumb|Tightly folded serpentinite from the [[Tux Alps]], Austria. Closeup view about {{convert|30|×|20|cm|abbr=on}}.]]
'''Serpentinite''' is a [[Rock (geology)|rock]] composed of one or more [[serpentine group]] [[mineral]]s, the name originating from the similarity of the texture of the rock to that of the skin of a snake.<ref name="Schoenherr2017">{{cite book|last=Schoenherr|first=Allan A.|title=A Natural History of California: Second Edition|url=https://books.google.com/books?id=Zj63DgAAQBAJ&pg=PA35|access-date=6 May 2017|date=2017-07-11|publisher=Univ of California Press|isbn=9780520295117|pages=35–}}</ref> Minerals in this group, which are rich in magnesium and water, light to dark green, greasy looking and slippery feeling, are formed by '''serpentinization''', a hydration and [[metamorphic rock|metamorphic]] transformation of [[ultramafic]] rock from the Earth's [[Mantle (geology)|mantle]]. The [[mineral alteration]] is particularly important at the [[sea floor]] at [[plate tectonics|tectonic plate]] boundaries.<ref name="GeologyDictionary">{{cite web |url=https://www.theodora.com/geology/glossarys.html#serpentine |title=Serpentine definition |work=Dictionary of Geology |access-date=2018-10-23}}</ref> Serpentinite has been called ''serpentine'' or ''serpentine rock'', particularly in older geological texts and in wider cultural settings.<ref name="MerrWeb">{{cite web | url=https://www.merriam-webster.com/dictionary/serpentine | title=serpentine | publisher=Merriam-Webster | work=Merriam-Webster.com Dictionary | access-date=6 March 2022}}</ref><ref name="leginfo.ca.gov">California Government Code § 425.2; ''see'' {{cite web |url=http://www.leginfo.ca.gov/cgi-bin/displaycode?section=gov&group=00001-01000&file=420-429.8 |title=CA Codes (Gov:420-429.8) |access-date=2009-12-24 |url-status=dead |archive-url=https://web.archive.org/web/20090628233244/http://www.leginfo.ca.gov/cgi-bin/displaycode?section=gov&group=00001-01000&file=420-429.8 |archive-date=28 June 2009 }}</ref><ref name="Oakeshott1968">{{cite journal | url=https://archives.datapages.com/data/specpubs/structu1/data/a153/a153/0001/0200/0228.htm | title=Diapiric Structures in Diablo Range, California | last=Oakeshott | first=G.B. | journal=AAPG Special Volume M8:Diapirism and Diapirs | date=1968 | volume=153 | pages=228–243}}</ref><ref name="Flett1913">{{cite journal | url=https://www.sciencedirect.com/science/article/abs/pii/S0016787813800089 | title=The geology of the lizard | last=Flett | first=J.S. | journal=Proceedings of the Geologists' Association | date=1913 | volume=24 | issue=3 | pages=118–133 | doi=10.1016/S0016-7878(13)80008-9}}</ref><ref name="González-Mancera_et_al_2003">{{cite journal | url=https://link.springer.com/article/10.1023/B:HYPE.0000003765.32151.3b | title=Mössbauer Study of Serpentine Minerals in the Ultramafic Body of Tehuitzingo, Southern Mexico | first1=G. | last1=González-Mancera | first2=F. |last2=Ortega-Gutiérrez | first3=N.E. | last3=Nava | first4=H.S. | last4=Arriola | journal=Hyperfine Interactions | date=2003 | volume=148 | issue=1–4 | pages=61–71 | doi=10.1023/B:HYPE.0000003765.32151.3b| bibcode=2003HyInt.148...61G | s2cid=96761317 }}</ref>
'''Serpentinite''' is a [[Rock (geology)|rock]] composed predominantly of one or more [[serpentine group]] [[mineral]]s, the name originating from the similarity of the texture of the rock to that of the skin of a snake.<ref name="Schoenherr2017">{{cite book|last=Schoenherr|first=Allan A.|title=A Natural History of California: Second Edition|url=https://books.google.com/books?id=Zj63DgAAQBAJ&pg=PA35|access-date=6 May 2017|date=2017-07-11|publisher=Univ of California Press|isbn=9780520295117|pages=35–}}</ref> Serpentinite has been called ''serpentine'' or ''serpentine rock'', particularly in older geological texts and in wider cultural settings.<ref name="MerrWeb">{{cite web | url=https://www.merriam-webster.com/dictionary/serpentine | title=serpentine | publisher=Merriam-Webster | work=Merriam-Webster.com Dictionary | access-date=6 March 2022}}</ref><ref name="leginfo.ca.gov">California Government Code § 425.2; ''see'' {{cite web |url=http://www.leginfo.ca.gov/cgi-bin/displaycode?section=gov&group=00001-01000&file=420-429.8 |title=CA Codes (Gov:420-429.8) |access-date=2009-12-24 |url-status=dead |archive-url=https://web.archive.org/web/20090628233244/http://www.leginfo.ca.gov/cgi-bin/displaycode?section=gov&group=00001-01000&file=420-429.8 |archive-date=28 June 2009 }}</ref><ref name="Oakeshott1968">{{cite journal | url=https://archives.datapages.com/data/specpubs/structu1/data/a153/a153/0001/0200/0228.htm | title=Diapiric Structures in Diablo Range, California | last=Oakeshott | first=G.B. | journal=AAPG Special Volume M8:Diapirism and Diapirs | date=1968 | volume=153 | pages=228–243}}</ref><ref name="Flett1913">{{cite journal | url=https://www.sciencedirect.com/science/article/abs/pii/S0016787813800089 | title=The geology of the lizard | last=Flett | first=J.S. | journal=Proceedings of the Geologists' Association | date=1913 | volume=24 | issue=3 | pages=118–133 | doi=10.1016/S0016-7878(13)80008-9}}</ref><ref name="González-Mancera_et_al_2003">{{cite journal | url=https://link.springer.com/article/10.1023/B:HYPE.0000003765.32151.3b | title=Mössbauer Study of Serpentine Minerals in the Ultramafic Body of Tehuitzingo, Southern Mexico | first1=G. | last1=González-Mancera | first2=F. |last2=Ortega-Gutiérrez | first3=N.E. | last3=Nava | first4=H.S. | last4=Arriola | journal=Hyperfine Interactions | date=2003 | volume=148 | issue=1–4 | pages=61–71 | doi=10.1023/B:HYPE.0000003765.32151.3b| bibcode=2003HyInt.148...61G | s2cid=96761317 }}</ref>


== Formation and petrology ==
== Formation and mineralogy ==
Serpentinite is formed by near to complete [[User:Kierabiner/sandbox SERPENTINIZATION|serpentinization]] of mafic to ultramafic rocks.<ref>{{Cite web |title=Introduction to Mineralogy and Petrology |url=https://www.sciencedirect.com/book/9780128205853/introduction-to-mineralogy-and-petrology |access-date=2022-11-20 |website=ScienceDirect |language=en}}</ref> Serpentinite can be formed wherever ultramafic rock is infiltrated by water poor in carbon dioxide.{{sfn|Moody|1976|p=136}} This occurs at [[mid-ocean ridges]] and in the [[forearc]] mantle of [[subduction zone]]s.<ref name=":2" /><ref name=":0">{{Cite journal |last=Albers |first=Elmar |last2=Bach |first2=Wolfgang |last3=Pérez-Gussinyé |first3=Marta |last4=McCammon |first4=Catherine |last5=Frederichs |first5=Thomas |date=2021 |title=Serpentinization-Driven H2 Production From Continental Break-Up to Mid-Ocean Ridge Spreading: Unexpected High Rates at the West Iberia Margin |url=https://www.frontiersin.org/articles/10.3389/feart.2021.673063 |journal=Frontiers in Earth Science |volume=9 |doi=10.3389/feart.2021.673063/full |issn=2296-6463}}</ref>
Serpentinization is a form of low-temperature [[metamorphism]] of [[ultramafic]] rocks, such as [[dunite]], [[harzburgite]], or [[lherzolite]]. These are rocks low in [[silica]] and composed mostly of [[olivine]] ({{chem2|(Mg(2+), Fe(2+))2SiO4}}), [[pyroxene]] ({{chem2|XY(Si,Al)2O6}}), and [[chromite]] (approximately {{chem2|FeCr2O4}}). Serpentinization is driven largely by [[Mineral hydration|hydration]] and [[oxidation]] of olivine and pyroxene to [[serpentine subgroup|serpentine]] minerals, [[brucite]] ({{chem2|Mg(OH)2}}), and [[magnetite]] ({{chem2|Fe3O4}}).<ref name=Moody1976>{{cite journal |last1=Moody |first1=Judith B. |title=Serpentinization: a review |journal=Lithos |date=April 1976 |volume=9 |issue=2 |pages=125–138 |doi=10.1016/0024-4937(76)90030-X|bibcode=1976Litho...9..125M }}</ref> Under the unusual chemical conditions accompanying serpentinization, water is the oxidizing agent, and is itself reduced to hydrogen, {{chem|[[hydrogen|H]]|2}}. This leads to further reactions that produce rare [[iron group]] [[native element mineral]]s, such as [[awaruite]] ({{chem|Ni|3|Fe}}) and [[native iron]];{{sfn|Moody|1976|p=129}} [[methane]] and other [[hydrocarbon]] compounds; and [[hydrogen sulfide]].<ref name=BerndtEtal1996>{{cite journal |last1=Berndt |first1=Michael E. |last2=Allen |first2=Douglas E. |last3=Seyfried |first3=William E. |title=Reduction of {{CO2}} during serpentinization of olivine at 300&nbsp;°C and 500 bar |journal=Geology |date=1 April 1996 |volume=24 |issue=4 |pages=351–354 |doi=10.1130/0091-7613(1996)024<0351:ROCDSO>2.3.CO;2|bibcode=1996Geo....24..351B }}</ref>


During serpentinization, large amounts of water are absorbed into the rock, increasing the volume, reducing the density and destroying the original structure.{{sfn|Moody|1976|p=128-129}}<ref name=LC>[http://www.lostcity.washington.edu/science/chemistry/serpentinization.html Serpentinization: The heat engine at Lost City and sponge of the oceanic crust]</ref> The density changes from {{convert|3.3|to|2.5|g/cm3|abbr=on}} with a concurrent volume increase on the order of 30-40%.<ref name=Mevel2003>{{cite journal |last1=Mével |first1=Catherine |title=Serpentinization of abyssal peridotites at mid-ocean ridges |journal=Comptes Rendus Geoscience |date=September 2003 |volume=335 |issue=10–11 |pages=825–852 |doi=10.1016/j.crte.2003.08.006|bibcode=2003CRGeo.335..825M }}</ref> The reaction is highly [[exothermic]] and rock temperatures can be raised by about {{convert|260|Celsius}},<ref name=LC/> providing an energy source for formation of non-volcanic [[hydrothermal vent]]s.<ref name=Lowell2002>{{cite journal |last1=Lowell |first1=R. P. |title=Seafloor hydrothermal systems driven by the serpentinization of peridotite |journal=Geophysical Research Letters |date=2002 |volume=29 |issue=11 |pages=1531 |doi=10.1029/2001GL014411|bibcode=2002GeoRL..29.1531L |doi-access=free }}</ref> The hydrogen, methane, and hydrogen sulfide produced during serpentinization are released at these vents and provide energy sources for deep sea [[chemotroph]] [[microorganism]]s.<ref name=FruhGreenEtal2004>{{cite journal |last1=Früh-Green |first1=Gretchen L. |last2=Connolly |first2=James A.D. |last3=Plas |first3=Alessio |last4=Kelley |first4=Deborah S. |last5=Grobéty |first5=Bernard |title=Serpentinization of oceanic peridotites: Implications for geochemical cycles and biological activity |journal=Geophysical Monograph Series |date=2004 |volume=144 |pages=119–136 |doi=10.1029/144GM08|bibcode=2004GMS...144..119F |isbn=0-87590-409-2 }}</ref><ref name=LC/>


The final mineral composition of serpentinite is usually dominated by [[lizardite]], [[chrysotile]], and magnetite. Brucite and [[antigorite]] are less commonly present. Lizardite, chrysotile, and antigorite all have approximately the formula {{chem2|Mg3(Si2O5)(OH)4}} or {{chem2|(Mg(2+), Fe(2+))3Si2O5(OH)4}}, but differ in minor components and in form.<ref name=":2">{{Cite book|last1=Roberts|first1=B. A.|url=https://books.google.com/books?id=Abb1CAAAQBAJ&dq=Lizardite&pg=PA11|title=The Ecology of Areas with Serpentinized Rocks: A World View|last2=Proctor|first2=J.|date=2012-12-06|publisher=Springer Science & Business Media|isbn=978-94-011-3722-5|language=en|page=8}}</ref> Accessory minerals, present in small quantities, include awaruite, other native metal minerals, and [[sulfide mineral]]s.<ref name=Moody1976/>


The final mineral composition of serpentinite is usually dominated by [[lizardite]], [[chrysotile]], and magnetite. Brucite and [[antigorite]] are less commonly present. Lizardite, chrysotile, and antigorite all have approximately the formula {{chem2|Mg3(Si2O5)(OH)4}} or {{chem2|(Mg(2+), Fe(2+))3Si2O5(OH)4}}, but differ in minor components and in form.<ref name=":2">{{Cite book|last1=Roberts|first1=B. A.|url=https://books.google.com/books?id=Abb1CAAAQBAJ&dq=Lizardite&pg=PA11|title=The Ecology of Areas with Serpentinized Rocks: A World View|last2=Proctor|first2=J.|date=2012-12-06|publisher=Springer Science & Business Media|isbn=978-94-011-3722-5|language=en|page=8}}</ref> Accessory minerals, present in small quantities, include awaruite, other native metal minerals, and [[sulfide mineral]]s.<ref name="Moody1976">{{cite journal |last1=Moody |first1=Judith B. |date=April 1976 |title=Serpentinization: a review |journal=Lithos |volume=9 |issue=2 |pages=125–138 |bibcode=1976Litho...9..125M |doi=10.1016/0024-4937(76)90030-X}}</ref>[[Image:Gros Morne moho.jpg|thumb|Ophiolite of the [[Gros Morne National Park]], Newfoundland. Ophiolites characteristically have a serpentinite component.]]
===Formation of serpentine minerals ===
Olivine is a [[solid solution]] of [[forsterite]], the [[magnesium]] endmember of {{chem2|(Mg(2+), Fe(2+))2SiO4}}, and [[fayalite]], the [[iron]] endmember, with forsterite typically making up about 90% of the olivine in ultramafic rocks.<ref name=SnowDick1995>{{cite journal |last1=Snow |first1=Jonathan E. |last2=Dick |first2=Henry J.B. |title=Pervasive magnesium loss by marine weathering of peridotite |journal=Geochimica et Cosmochimica Acta |date=October 1995 |volume=59 |issue=20 |pages=4219–4235 |doi=10.1016/0016-7037(95)00239-V|bibcode=1995GeCoA..59.4219S }}</ref> Serpentinite can form from [[olivine]] via several reactions:


=== Hydrothermal vents and mud volcanoes ===
{{NumBlk|:
|{{overset|[[Forsterite]]|3 {{chem|Mg|2|SiO|4}}}} + {{overset|silicon dioxide|{{chem|SiO|2}}}} + 4 {{chem|H|2|O}} → {{overset|serpentine|2 {{chem|Mg|3|Si|2|O|5|(OH)|4}}}}
|{{EquationRef|Reaction 1a}}}}

{{NumBlk|:
|{{overset|[[Forsterite]]|2 {{chem|Mg|2|SiO|4}}}} + {{overset|water|3 {{chem|H|2|O}}}} → {{overset|serpentine|{{chem|Mg|3|Si|2|O|5|(OH)|4}}}} + {{overset|[[brucite]]|{{chem|Mg|(OH)|2}}}}
|{{EquationRef|Reaction 1b}}}}

Reaction 1a tightly binds silica, lowering its [[chemical activity]] to the lowest values seen in common rocks of the [[Earth's crust]].<ref name=FrostBeard2007>{{cite journal |last1=Frost |first1=B. R. |last2=Beard |first2=J. S. |title=On Silica Activity and Serpentinization |journal=Journal of Petrology |date=3 April 2007 |volume=48 |issue=7 |pages=1351–1368 |doi=10.1093/petrology/egm021|url=http://petrology.oxfordjournals.org/content/48/7/1351.full.pdf }}</ref> Serpentinization then continues through the hydration of olivine to yield serpentine and brucite (Reaction 1b).<ref name="Coleman77">{{cite book|last=Coleman|first=Robert G.|title=Ophiolites|date=1977|publisher=Springer-Verlag|isbn=978-3540082767|pages=100–101}}</ref> The mixture of brucite and serpentine formed by Reaction 1b has the lowest silica activity in the serpentinite, so that the brucite phase is very important in understanding serpentinization.<ref name=FrostBeard2007/> However, the brucite is often blended in with the serpentine such that it is difficult to identify except with [[X-ray diffraction]], and it is easily altered under surface weathering conditions.{{sfn|Moody|1976|p=127}}

A similar suite of reactions involves [[pyroxene]]-group minerals:

{{NumBlk|:
|{{overset|[[Enstatite]]|3 {{chem|Mg|SiO|3}}}} + {{overset|silicon dioxide|{{chem|SiO|2}}}} + {{chem|H|2|O}} → {{overset|[[talc]]|{{chem|Mg|3|Si|4|O|10|(OH)|2}}}}
|{{EquationRef|Reaction 2a}}}}

{{NumBlk|:
|{{overset|[[Enstatite]]|6 {{chem|Mg|SiO|3}}}} + 3 {{chem|H|2|O}} → {{overset|serpentine|{{chem|Mg|3|Si|2|O|5|(OH)|4}}}} + {{overset|[[talc]]|{{chem|Mg|3|Si|4|O|10|(OH)|2}}}}
|{{EquationRef|Reaction 2b}}}}

Reaction 2a quickly comes to a halt as silica becomes unavailable, and Reaction 2b takes over.{{sfn|Frost|Beard|2007|p=1355}} When olivine is abundant, silica activity drops low enough that talc begins to react with olivine:

{{NumBlk|:
|{{overset|[[Forsterite]]|6 {{chem|Mg|2|SiO|4}}}} + {{overset|[[talc]]|{{chem|Mg|3|Si|4|O|10|(OH)|2}}}} + {{overset|water|9 {{chem|H|2|O}}}} → {{overset|serpentine|5 {{chem|Mg|3|Si|2|O|5|(OH)|4}}}}
|{{EquationRef|Reaction 3}}}}

This reaction requires higher temperatures than those at which brucite forms.{{sfn|Moody|1976|p=127}}

The final mineralogy depends both on rock and fluid compositions, temperature, and pressure. Antigorite forms in reactions at temperatures that can exceed {{convert|600|C|F|abbr=on}} 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.{{sfn|Moody|1976|p=125, 127, 131}}

===Breakdown of diopside and formation of rodingites===
Ultramafic rocks often contain calcium-rich pyroxene ([[diopside]]), which breaks down according to the reaction

{{NumBlk|:
|{{overset|[[Diopside]]|3 {{chem|Ca|Mg|Si|2|O|6}}}} + 6 {{chem|H|+}} → {{overset|serpentine|{{chem|Mg|3|Si|2|O|5|(OH)|4}}}} + 3 {{chem|Ca|2+}} + {{chem|H|2|O}} + {{overset|silicon dioxide|4 {{chem|SiO|2}}}}
|{{EquationRef|Reaction 4}}}}

This raises both the [[pH]], often to very high values, and the calcium content of the fluids involved in serpentinization. These fluids are highly reactive and may transport [[calcium]] and other elements into surrounding [[mafic]] rocks. Fluid reaction with these rocks may create [[metasomatism|metasomatic]] reaction zones enriched in calcium and depleted in silica, called [[rodingite]]s.{{sfn|Frost|Beard|2007|pp=1360-1362}}

===Formation of magnetite and hydrogen===
In most crustal rock, the chemical activity of oxygen is prevented from dropping to very low values by the [[Mineral redox buffer#Common redox buffers and mineralogy|fayalite-magnetite-quartz (FMQ) buffer]].{{sfn|Moody|1976|p=129}} The very low chemical activity of silica during serpentinization eliminates this buffer, allowing serpentinization to produce highly [[Reduction (chemistry)|reducing]] conditions.<ref name=FrostBeard2007/> Under these conditions, water is capable of oxidizing ferrous ({{chem|Fe|2+}}) ions in fayalite. The process is of interest because it generates hydrogen gas:<ref>{{cite web| title = Methane and hydrogen formation from rocks – Energy sources for life| url = http://www.lostcity.washington.edu/science/chemistry/methane.html| access-date = 2011-11-06}}</ref><ref>{{Cite journal| last = Sleep| first = N.H.| author2 = A. Meibom, Th. Fridriksson, R.G. Coleman, D.K. Bird| year = 2004| title = H<sub>2</sub>-rich fluids from serpentinization: Geochemical and biotic implications| journal = Proceedings of the National Academy of Sciences of the United States of America| volume = 101| issue = 35| pages = 12818–12823| doi = 10.1073/pnas.0405289101|bibcode = 2004PNAS..10112818S| pmid=15326313| pmc=516479| doi-access = free}}</ref>

{{NumBlk|:
|{{overset|[[Fayalite]]|3 {{chem|Fe|2|SiO|4}}}} + {{overset|water|2 {{chem|H|2|O}}}} → {{overset|[[magnetite]]|2 {{chem|Fe|3|O|4}}}} + {{overset|silicon dioxide|3 {{chem|SiO|2}}}} + {{overset|hydrogen|2 {{chem|H|2}}}}
|{{EquationRef|Reaction 5}}}}

However, studies of serpentinites suggest that iron minerals are first converted to [[wikt:ferroan|ferroan]] brucite, that is, brucite containing {{chem2|Fe(OH)2}},<ref>{{cite journal |last1=Bach |first1=Wolfgang |last2=Paulick |first2=Holger |last3=Garrido |first3=Carlos J. |last4=Ildefonse |first4=Benoit |last5=Meurer |first5=William P. |last6=Humphris |first6=Susan E. |title=Unraveling the sequence of serpentinization reactions: petrography, mineral chemistry, and petrophysics of serpentinites from MAR 15°N (ODP Leg 209, Site 1274) |journal=Geophysical Research Letters |date=2006 |volume=33 |issue=13 |pages=L13306 |doi=10.1029/2006GL025681|bibcode=2006GeoRL..3313306B |hdl=1912/3324 |s2cid=55802656 |hdl-access=free }}</ref> which then undergoes the [[Schikorr reaction]] in the anaerobic conditions of serpentinization:<ref name=Esource>{{cite journal |doi=10.1111/j.1472-4669.2010.00249.x|title=Serpentinization as a source of energy at the origin of life|year=2010|last1=Russell|first1=M. J.|last2=Hall|first2=A. J.|last3=Martin|first3=W.|journal=Geobiology|volume=8|issue=5|pages=355–371|pmid=20572872|s2cid=41118603 }}</ref><ref>{{cite journal |doi=10.2138/rmg.2013.75.18|title=Serpentinization, Carbon, and Deep Life|year=2013|last1=Schrenk|first1=M. O.|last2=Brazelton|first2=W. J.|last3=Lang|first3=S. Q.|journal=Reviews in Mineralogy and Geochemistry|volume=75|issue=1|pages=575–606|bibcode=2013RvMG...75..575S}}</ref>

{{NumBlk|:
|{{underset|ferrous hydroxide|6 {{chem|Fe|(OH)|2}}}} → {{underset|magnetite|2 {{chem|Fe|3|O|4}}}} + {{underset|water|4 {{chem|H|2|O}}}} + {{underset|hydrogen|2 {{chem|H|2}}}}
|{{EquationRef|Reaction 6}}}}

Maximum reducing conditions, and the maximum rate of production of hydrogen, occur when the temperature of serpentinization is between {{convert|200 and 315|C||sp=us}}.<ref>{{cite journal |last1=McCollom |first1=Thomas M. |last2=Bach |first2=Wolfgang |title=Thermodynamic constraints on hydrogen generation during serpentinization of ultramafic rocks |journal=Geochimica et Cosmochimica Acta |date=February 2009 |volume=73 |issue=3 |pages=856–875 |doi=10.1016/j.gca.2008.10.032|bibcode=2009GeCoA..73..856M }}</ref> If the original ultramafic rock (the ''[[protolith]]'') is peridotite, which is rich in olivine, considerable magnetite and hydrogen are produced. When the protolith is pyroxenite, which contains more pyroxene than olivine, iron-rich talc is produced with no magnetite and only modest hydrogen production. Infiltration of silica-bearing fluids during serpentinization can suppress both the formation of brucite and the subsequent production of hydrogen.<ref>{{cite journal |last1=Klein |first1=Frieder |last2=Bach |first2=Wolfgang |last3=McCollom |first3=Thomas M. |title=Compositional controls on hydrogen generation during serpentinization of ultramafic rocks |journal=Lithos |date=September 2013 |volume=178 |pages=55–69 |doi=10.1016/j.lithos.2013.03.008|bibcode=2013Litho.178...55K }}</ref>

Chromite present in the protolith will be altered to chromium-rich magnetite at lower serpentinization temperatures. At higher temperatures, it will be altered to iron-rich chromite (ferrit-chromite).{{sfn|Moody|1967|p=128}} During serpentinization, the rock is enriched in [[chlorine]], [[boron]], [[fluorine]], and sulfur. Sulfur will be reduced to hydrogen sulfide and sulfide minerals, though significant quantities are incorporated into serpentine minerals, and some may later be reoxidized to sulfate minerals such as [[anhydrite]].<ref name=Mevel2003/> The sulfides produced include nickel-rich sulfides, such as [[mackinawite]].<ref>{{cite journal |last1=Delacour |first1=Adélie |last2=Früh-Green |first2=Gretchen L. |last3=Bernasconi |first3=Stefano M. |title=Sulfur mineralogy and geochemistry of serpentinites and gabbros of the Atlantis Massif (IODP Site U1309) |journal=Geochimica et Cosmochimica Acta |date=October 2008 |volume=72 |issue=20 |pages=5111–5127 |doi=10.1016/j.gca.2008.07.018|bibcode=2008GeCoA..72.5111D }}</ref>

===Methane and other hydrocarbons===
Laboratory experiments have confirmed that at a temperature of {{convert|300|C||sp=us}} and pressure of 500 bars, olivine serpentinizes with release of hydrogen gas. In addition, methane and complex hydrocarbons are formed through reduction of carbon dioxide. The process may be catalyzed by magnetite formed during serpentinization.<ref name=BerndtEtal1996/> One reaction pathway is:<ref name=Esource/>

{{NumBlk|:
|{{overset|forsterite|18 {{chem|Mg|2|SiO|4}}}} + {{overset|fayalite|6 {{chem|Fe|2|SiO|4}}}} + 26 {{chem|H|2|O}} + {{chem|CO|2}} → {{overset|serpentine|12 {{chem|Mg|3|Si|2|O|5|(OH)|4}}}} + {{overset|magnetite|4 {{chem|Fe|3|O|4}}}} + {{overset|methane|{{chem|CH|4}}}}
|{{EquationRef|Reaction 7}}}}

===Metamorphism at higher pressure and temperature===
Lizardite and chrysotile are stable at low temperatures and pressures, while antigorite is stable at higher temperatures and pressure. Its presence in a serpentinite indicates either that serpentinization took place at unusually high pressure and temperature or that the rock experienced higher grade metamorphism after serpentinization was complete.{{sfn|Moody|1976|p=125, 127, 131}}

Infiltration of {{CO2}}-bearing fluids into serpentinite causes distinctive ''[[Talc carbonate|talc-carbonate alteration]]''. Brucite rapidly converts to [[magnesite]] and serpentine minerals (other than antigorite) are converted to talc. The presence of [[pseudomorph]]s of the original serpentinite minerals shows that this alteration takes place after serpentinization.{{sfn|Moody|1976|p=133}}

Serpentinite may contain [[chlorite group|chlorite]] (a [[phyllosilicate]] mineral), [[tremolite]] (Ca<sub>2</sub>(Mg<sub>5.0-4.5</sub>Fe<sup>2+</sup><sub>0.0-0.5</sub>)Si<sub>8</sub>O<sub>22</sub>(OH)<sub>2</sub>), and metamorphic olivine and [[diopside]] (calcium-rich pyroxene). This indicates that the serpentinite has been subject to more intense metamorphism, reaching the upper [[greenschist]] or [[amphibolite]] [[metamorphic facies]].{{sfn|Moody|1976|p=128}}

Above about {{convert|450|C||sp=us}}, antigorite begins to break down. Thus serpentinite does not exist at higher metamorphic facies.<ref name=FruhGreenEtal2004/>

===Extraterrestrial production of methane by serpentinization===
The presence of traces of [[Methane on Mars|methane in the atmosphere of Mars]] has been hypothesized to be a possible evidence for [[life on Mars (planet)|life on Mars]] if methane was produced by [[bacteria]]l activity. Serpentinization has been proposed as an alternative non-biological source for the observed methane traces.<ref>{{cite journal|jstor=27858733|title=Life on Mars?|date=March–April 2006|journal=American Scientist|volume=94|issue=2|pages=119–120|last1=Baucom|first1=Martin|doi=10.1511/2006.58.119}}</ref><ref>{{Cite web|url=https://www.esa.int/Our_Activities/Human_and_Robotic_Exploration/Exploration/ExoMars/The_methane_mystery|title=The methane mystery|last=esa|website=European Space Agency|language=en-GB|access-date=2019-04-22}}</ref> In 2022 it was reported that microscopic examination of the [[ALH 84001]] meteorite, which came from Mars, shows that indeed the organic matter it contains was formed by serpentinization, not by life processes.<ref>{{cite journal |display-authors=etal|last1=Andrew Steele |title=Organic synthesis associated with serpentinization and carbonation on early Mars |journal=Science |date=13 January 2022 |volume=375 |issue=6577 |pages=172–177 |doi=10.1126/science.abg7905|pmid=35025630 |bibcode=2022Sci...375..172S |s2cid=245933224 }}</ref><ref>{{cite journal |last1=Leah Crane |title=Mars: Organic compounds were made by water interacting with rocks |journal=New Scientist |date=22 January 2022 |url=https://www.newscientist.com/article/2304270-organic-compounds-on-mars-were-produced-by-water-and-rocks-not-life/}}</ref>

Using data from the [[Cassini–Huygens|Cassini]] probe flybys obtained in 2010–12, scientists were able to confirm that Saturn's moon [[Enceladus]] likely has a liquid water ocean beneath its frozen surface. A model suggests that the ocean on Enceladus has an alkaline [[pH]] of 11–12.<ref name="pH 2015">{{cite journal |title=The pH of Enceladus' ocean |journal=Geochimica et Cosmochimica Acta |date=16 April 2015 |last1=R. Glein |first1=Christopher |last2= Baross |first2= John A. |last3=Waite |first3=Hunter |doi=10.1016/j.gca.2015.04.017 |bibcode=2015GeCoA.162..202G |volume=162 |pages=202–219|arxiv=1502.01946 |s2cid=119262254 }}</ref> The high pH is interpreted to be a key consequence of serpentinization of [[chondrite|chondritic rock]], that leads to the generation of {{chem|H|2}}, a geochemical source of energy that can support both abiotic and biological synthesis of organic molecules.<ref name="pH 2015"/><ref>{{cite news |last=Wall |first=Mike |url=http://www.space.com/29334-enceladus-ocean-energy-source-life.html |title=Ocean on Saturn Moon Enceladus May Have Potential Energy Source to Support Life |work=Space.com |date=7 May 2015 |access-date=2015-05-08 }}</ref>

==Occurrence==
[[Image:Gros Morne moho.jpg|thumb|Ophiolite of the [[Gros Morne National Park]], Newfoundland. Ophiolites characteristically have a serpentinite component.]]
Serpentinite can be formed wherever ultramafic rock is infiltrated by water poor in carbon dioxide.{{sfn|Moody|1976|p=136}} This occurs at [[mid-ocean ridges]] and in the [[forearc]] mantle of [[subduction zone]]s.

Conditions are highly favorable for serpentinization at slow to ultraslow spreading mid-ocean ridges.<ref name=Mevel2003/> Here the rate of [[crustal extension]] is high compared with the volume of magmatism, bringing ultramafic mantle rock very close to the surface where fracturing allows seawater to infiltrate the rock.<ref name=Lowell2002/>

Serpentinized ultramafic rock is found in many [[ophiolite]]s. Ophiolites are fragments of oceanic [[lithosphere]] that has been thrust onto continents, a process called ''[[obduction]]''. They typically consist of a layer of serpentinized harzburgite (sometimes called ''alpine peridotite'' in older writings), a layer of hydrothermally altered [[diabase]]s and [[pillow basalt]]s, and a layer of deep water sediments containing radiolarian ribbon [[chert]].<ref>{{cite book |last1=Philpotts |first1=Anthony R. |last2=Ague |first2=Jay J. |title=Principles of igneous and metamorphic petrology |date=2009 |publisher=Cambridge University Press |location=Cambridge, UK |isbn=9780521880060 |edition=2nd |pages=370–372}}</ref>

Serpentinization is nearly total in the forearc mantle of subduction zones. Here mantle rock is cooled by the subducting slab to temperatures at which serpentinite is stable, and fluids are released from the subducting slab in great quantities into the ultramafic mantle rock. Direct evidence that serpentinization is taking place in the [[Mariana Islands]] [[island arc]] is provided by the activity of serpentinite [[mud volcano]]es. [[Xenolith]]s of harzburgite and (less commonly) dunite are occasionally erupted by the mud volcanoes, giving clues to the nature of the protolith.<ref name=HyndmanPeacock2003>{{cite journal |last1=Hyndman |first1=Roy D |last2=Peacock |first2=Simon M |title=Serpentinization of the forearc mantle |journal=Earth and Planetary Science Letters |date=July 2003 |volume=212 |issue=3–4 |pages=417–432 |doi=10.1016/S0012-821X(03)00263-2|bibcode=2003E&PSL.212..417H }}</ref>

Because serpentinization increases the volume and lowers the density of the original rock, serpentinitization may lead to uplift that creates coastal ranges above mantle forearcs.<ref name=HyndmanPeacock2003/> Further uplift can bring serpentinite to the surface when subduction ceases, as has taken place with the serpentinite exposed at the [[Presidio of San Francisco]].<ref name="Presidio">{{cite web |title=Serpentinite |url=https://www.nps.gov/prsf/learn/nature/serpentinite.htm |website=Presidio of San Francisco |publisher=National Park Service |access-date=3 September 2021}}</ref>

[[Seismic wave]] studies can detect the presence of large bodies of serpentinite in the crust and upper mantle, since serpentinization lowers seismic wave velocities. This is particularly true of S waves, due to the high value of [[Poisson's ratio]] for serpentinites. Seismic measurements confirm that serpentinization is pervasive in forearc mantle.<ref name=HyndmanPeacock2003/> The serpentization can produce an inverted [[Moho discontinuity]], in which seismic velocity abruptly ''decreases'' across the crust-mantle boundary, which is the opposite of the usual behavior. The serpentinite is highly deformable, creating an aseismic zone in the forearc, and the presence of serpentinite may limit the maximum depth of [[megathrust earthquake]]s.<ref>{{cite journal |last1=Bostock |first1=M. G. |last2=Hyndman |first2=R. D. |last3=Rondenay |first3=S. |last4=Peacock |first4=S. M. |title=An inverted continental Moho and serpentinization of the forearc mantle |journal=Nature |date=May 2002 |volume=417 |issue=6888 |pages=536–538 |doi=10.1038/417536a|pmid=12037564 |bibcode=2002Natur.417..536B |s2cid=3113794 }}</ref> Serpentinization at slow spreading mid-ocean ridges can cause the seismic Moho discontinuity to be placed at the serpentinization front, rather than the base of the crust as defined by normal petrological criteria.<ref>{{cite journal |last1=Minshull |first1=T. A. |last2=Muller |first2=M. R. |last3=Robinson |first3=C. J. |last4=White |first4=R. S. |last5=Bickle |first5=M. J. |title=Is the oceanic Moho a serpentinization front? |journal=Geological Society, London, Special Publications |date=1998 |volume=148 |issue=1 |pages=71–80 |doi=10.1144/GSL.SP.1998.148.01.05|bibcode=1998GSLSP.148...71M |s2cid=128410328 }}</ref><ref name=Mevel2003/> The Lanzo Massif of the Italian Alps shows a sharp serpentinization front that may be a relict seismic Moho.<ref>{{cite journal |last1=Debret |first1=B. |last2=Nicollet |first2=C. |last3=Andreani |first3=M. |last4=Schwartz |first4=S. |last5=Godard |first5=M. |title=Three steps of serpentinization in an eclogitized oceanic serpentinization front (Lanzo Massif - Western Alps): ECLOGITIZED SERPENTINIZATION FRONT (LANZO) |journal=Journal of Metamorphic Geology |date=February 2013 |volume=31 |issue=2 |pages=165–186 |doi=10.1111/jmg.12008|s2cid=140540631 }}</ref>

Notable occurrences of serpentinite are found at [[Thetford Mines]], [[Quebec]]; [[Lake Valhalla]], [[New Jersey]]; [[Gila County, Arizona]]; [[Lizard complex]], Lizard Point, Cornwall; and in localities in Greece, Italy, and other parts of Europe.<ref>{{cite book |last1=Sinkankas |first1=John |title=Mineralogy for amateurs. |date=1964 |publisher=Van Nostrand |location=Princeton, N.J. |isbn=0442276249|pages=149–480}}</ref> Notable ophiolites containing serpentinite include the [[Semail Ophiolite]] of Oman, the [[Troodos Ophiolite]] of [[Cyprus]], the [[Newfoundland]] ophiolites, and the Main Ophiolite Belt of [[New Guinea]].{{sfn|Philpotts|Ague|2009|p=371}}

== Hydrothermal vents and mud volcanoes ==
[[File:Expl2224_-_Flickr_-_NOAA_Photo_Library.jpg |thumb|A white carbonate spire in the Lost City vent field]]
[[File:Expl2224_-_Flickr_-_NOAA_Photo_Library.jpg |thumb|A white carbonate spire in the Lost City vent field]]
Deep sea hydrothermal vents located on serpentinite close to the axis of mid-ocean ridges generally resemble [[black smoker]]s located on basalt, but emit complex hydrocarbon molecules. The Rainbow field of the Mid-Atlantic Ridge is an example of such hydrothermal vents. Serpentinization alone cannot provide the heat supply for these vents, which must be driven mostly by magmatism. However, the [[Lost City Hydrothermal Field]], located off the axis of the Mid-Atlantic Ridge, may be driven solely by heat of serpentinization. Its vents are unlike black smokers, emitting relatively cool fluids ({{convert|40 to 75|C||sp=us}}) that are highly alkaline, high in magnesium, and low in hydrogen sulfide. The vents build up very large chimneys, up to {{convert|60|m||sp=us}} in height, composed of carbonate minerals and brucite. Lush microbial communities are associated with the vents. Though the vents themselves are not composed of serpentinite, they are hosted in serpentinite estimated to have formed at a temperature of about {{convert|200|C||sp=us}}.<ref name=":1" /> [[Sepiolite]] deposits on mid-ocean ridges may have formed through serpentinite-driven hydrothermal activity.<ref name="Mevel2003">{{cite journal |last1=Mével |first1=Catherine |date=September 2003 |title=Serpentinization of abyssal peridotites at mid-ocean ridges |journal=Comptes Rendus Geoscience |volume=335 |issue=10–11 |pages=825–852 |bibcode=2003CRGeo.335..825M |doi=10.1016/j.crte.2003.08.006}}</ref> However, geologists continue to debate whether serpentinization alone can account for the heat flux from the Lost City field.<ref name=":1">{{cite journal |last1=Allen |first1=Douglas E. |last2=Seyfried |first2=W.E. |title=Serpentinization and heat generation: constraints from Lost City and Rainbow hydrothermal systems 1 1Associate editor: J. C. Alt |journal=Geochimica et Cosmochimica Acta |date=March 2004 |volume=68 |issue=6 |pages=1347–1354 |doi=10.1016/j.gca.2003.09.003}}</ref>
The formation of serpentinite is highly exothermic, releasing up to {{convert|40|kJ|kcal|sp=us}} per mole of water reacting with the rock. This corresponds to a release of about 660 MJ/m<sup>3</sup> and can raise the rock temperature by about {{convert|260|Celsius}},<ref name=FruhGreenEtal2004/> providing an energy source for formation of non-volcanic hydrothermal vents.<ref name=Lowell2002/> The hydrogen, methane, and hydrogen sulfide produced during serpentinization are released at these vents and provide energy sources for deep sea [[chemotroph]] [[microorganism]]s.<ref name=FruhGreenEtal2004/><ref name=LC/>

Deep sea hydrothermal vents located on serpentinite close to the axis of mid-ocean ridges generally resemble [[black smoker]]s located on basalt, but emit complex hydrocarbon molecules. The Rainbow field of the Mid-Atlantic Ridge is an example of such hydrothermal vents. Serpentinization alone cannot provide the heat supply for these vents, which must be driven mostly by magmatism. However, the [[Lost City Hydrothermal Field]], located off the axis of the Mid-Atlantic Ridge, may be driven solely by heat of serpentinization. Its vents are unlike black smokers, emitting relatively cool fluids ({{convert|40 to 75|C||sp=us}}) that are highly alkaline, high in magnesium, and low in hydrogen sulfide. The vents build up very large chimneys, up to {{convert|60|m||sp=us}} in height, composed of carbonate minerals and brucite. Lush microbial communities are associated with the vents. Though the vents themselves are not composed of serpentinite, they are hosted in serpentinite estimated to have formed at a temperature of about {{convert|200|C||sp=us}}. [[Sepiolite]] deposits on mid-ocean ridges may have formed through serpentinite-driven hydrothermal activity.<ref name=Mevel2003/> However, geologists continue to debate whether serpentinization alone can account for the heat flux from the Lost City field.<ref>{{cite journal |last1=Allen |first1=Douglas E. |last2=Seyfried |first2=W.E. |title=Serpentinization and heat generation: constraints from Lost City and Rainbow hydrothermal systems 1 1Associate editor: J. C. Alt |journal=Geochimica et Cosmochimica Acta |date=March 2004 |volume=68 |issue=6 |pages=1347–1354 |doi=10.1016/j.gca.2003.09.003}}</ref>


The forearc of the Marianas subduction zone hosts large serpentinite mud volcanoes, which erupt serpentinite mud that rises through faults from the underlying serpentinized forearc mantle. Study of these mud volcanoes gives insights into subduction processes, and the high pH fluids emitted at the volcanoes support a microbial community.<ref name=Fryer2012>{{cite journal |last1=Fryer |first1=Patricia |title=Serpentinite Mud Volcanism: Observations, Processes, and Implications |journal=Annual Review of Marine Science |date=15 January 2012 |volume=4 |issue=1 |pages=345–373 |doi=10.1146/annurev-marine-120710-100922 |pmid=22457979 |bibcode=2012ARMS....4..345F |language=en |issn=1941-1405}}</ref>
The forearc of the Marianas subduction zone hosts large serpentinite mud volcanoes, which erupt serpentinite mud that rises through faults from the underlying serpentinized forearc mantle. Study of these mud volcanoes gives insights into subduction processes, and the high pH fluids emitted at the volcanoes support a microbial community.<ref name=Fryer2012>{{cite journal |last1=Fryer |first1=Patricia |title=Serpentinite Mud Volcanism: Observations, Processes, and Implications |journal=Annual Review of Marine Science |date=15 January 2012 |volume=4 |issue=1 |pages=345–373 |doi=10.1146/annurev-marine-120710-100922 |pmid=22457979 |bibcode=2012ARMS....4..345F |language=en |issn=1941-1405}}</ref><ref name=":0" />


Serpentinite thermal vents are a candidate for the environment in which life on Earth originated.<ref name=Fryer2012/> Most of the chemical reactions necessary to synthesize [[acetyl-CoA]], essential to basic biochemical pathways of life, take place during serpentinization.<ref>{{cite journal |last1=Martin |first1=William |last2=Russell |first2=Michael J |title=On the origin of biochemistry at an alkaline hydrothermal vent |journal=Philosophical Transactions of the Royal Society B: Biological Sciences |date=29 October 2007 |volume=362 |issue=1486 |pages=1887–1926 |doi=10.1098/rstb.2006.1881|pmid=17255002 |pmc=2442388 }}</ref> The sulfide-metal clusters that activate many enzymes resemble sulfide minerals formed during serpentinization.<ref>{{cite journal |last1=McCollom |first1=T. M. |last2=Seewald |first2=J. S. |title=Serpentinites, Hydrogen, and Life |journal=Elements |date=1 April 2013 |volume=9 |issue=2 |pages=129–134 |doi=10.2113/gselements.9.2.129 |citeseerx=10.1.1.852.2089 }}</ref>
Serpentinite thermal vents are a candidate for the environment in which life on Earth originated.<ref name=Fryer2012/> Most of the chemical reactions necessary to synthesize [[acetyl-CoA]], essential to basic biochemical pathways of life, take place during serpentinization.<ref>{{cite journal |last1=Martin |first1=William |last2=Russell |first2=Michael J |title=On the origin of biochemistry at an alkaline hydrothermal vent |journal=Philosophical Transactions of the Royal Society B: Biological Sciences |date=29 October 2007 |volume=362 |issue=1486 |pages=1887–1926 |doi=10.1098/rstb.2006.1881|pmid=17255002 |pmc=2442388 }}</ref> The sulfide-metal clusters that activate many enzymes resemble sulfide minerals formed during serpentinization.<ref>{{cite journal |last1=McCollom |first1=T. M. |last2=Seewald |first2=J. S. |title=Serpentinites, Hydrogen, and Life |journal=Elements |date=1 April 2013 |volume=9 |issue=2 |pages=129–134 |doi=10.2113/gselements.9.2.129 |citeseerx=10.1.1.852.2089 |url=https://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.852.2089&rep=rep1&type=pdf |access-date=5 September 2021}}</ref>


Experimental drilling into the [[gabbro]] layer of oceanic crust near mid-ocean ridges has demonstrated the presence of a sparse population of hydrocarbon-degrading [[bacteria]]. These may feed on hydrocarbons produced by serpentinization of the underlying ultramafic rock.<ref>{{cite journal |last1=Mason |first1=Olivia U. |last2=Nakagawa |first2=Tatsunori |last3=Rosner |first3=Martin |last4=Van Nostrand |first4=Joy D. |last5=Zhou |first5=Jizhong |last6=Maruyama |first6=Akihiko |last7=Fisk |first7=Martin R. |last8=Giovannoni |first8=Stephen J. |title=First Investigation of the Microbiology of the Deepest Layer of Ocean Crust |journal=PLOS ONE|date=5 November 2010 |volume=5 |issue=11 |pages=e15399 |pmc=2974637 | doi=10.1371/journal.pone.0015399|pmid=21079766 |bibcode=2010PLoSO...515399M |doi-access=free }}</ref><ref>{{cite news |last1=Marshall |first1=Michael |title=Life is found in deepest layer of Earth's crust |url=https://www.newscientist.com/article/mg20827874-800-life-is-found-in-deepest-layer-of-earths-crust/?ignored=irrelevant |access-date=3 December 2021 |work=New Scientist |date=17 November 2010}}</ref>
Experimental drilling into the [[gabbro]] layer of oceanic crust near mid-ocean ridges has demonstrated the presence of a sparse population of hydrocarbon-degrading [[bacteria]]. These may feed on hydrocarbons produced by serpentinization of the underlying ultramafic rock.<ref>{{cite journal |last1=Mason |first1=Olivia U. |last2=Nakagawa |first2=Tatsunori |last3=Rosner |first3=Martin |last4=Van Nostrand |first4=Joy D. |last5=Zhou |first5=Jizhong |last6=Maruyama |first6=Akihiko |last7=Fisk |first7=Martin R. |last8=Giovannoni |first8=Stephen J. |title=First Investigation of the Microbiology of the Deepest Layer of Ocean Crust |journal=PLOS ONE|date=5 November 2010 |volume=5 |issue=11 |pages=e15399 |pmc=2974637 | doi=10.1371/journal.pone.0015399|pmid=21079766 |bibcode=2010PLoSO...515399M |doi-access=free }}</ref><ref>{{cite news |last1=Marshall |first1=Michael |title=Life is found in deepest layer of Earth's crust |url=https://www.newscientist.com/article/mg20827874-800-life-is-found-in-deepest-layer-of-earths-crust/?ignored=irrelevant |access-date=3 December 2021 |work=New Scientist |date=17 November 2010}}</ref>


==Ecology==
== Ecology ==
[[File:Landscape, south of New Caledonia.jpg|thumb|upright=1.15|Serpentinite ecosystem in the south of New Caledonia]]
[[File:Landscape, south of New Caledonia.jpg|thumb|upright=1.15|Serpentinite ecosystem in the south of New Caledonia]]
{{main|Serpentine soil}}
{{main|Serpentine soil}}
Soil cover over serpentinite bedrock tends to be thin or absent. Soil with serpentine is poor in calcium and other major plant nutrients, but rich in elements toxic to plants such as chromium and nickel.<ref>[http://vulcan.wr.usgs.gov/LivingWith/VolcanicPast/Notes/serpentine.html "CVO Website - Serpentine and serpentinite"] {{webarchive|url=https://web.archive.org/web/20111019015059/http://vulcan.wr.usgs.gov/LivingWith/VolcanicPast/Notes/serpentine.html |date=19 October 2011 }}, ''USGS/NPS Geology in the Parks Website'', September 2001, accessed 27 February 2011.</ref> Some species of plants, such as ''[[Clarkia franciscana]]'' and certain species of [[manzanita]], are adapted to living on serpentinite outcrops. However, because serpentinite outcrops are few and isolated, their plant communities are [[ecological island]]s and these distinctive species are often highly endangered.<ref name="Presidio"/> On the other hand, plant communities adapted to living on the serpentine outcrops of [[New Caledonia]] resist displacement by [[introduced species]] that are poorly adapted to this environment.<ref name="futura1">{{cite web|url=http://www.futura-sciences.com/fr/doc/t/zoologie-1/r/nouvelle-caledonie/d/la-faune-et-la-flore-de-nouvelle-caledonie_468/c3/221/p2/ |title=La flore de Nouvelle-Calédonie – Première partie |website=Futura-sciences.com |date=2004-08-18 |access-date=2013-01-30}}</ref>
Soil cover over serpentinite bedrock tends to be thin or absent. Soil with serpentine is poor in calcium and other major plant nutrients, but rich in elements toxic to plants such as chromium and nickel.<ref>[http://vulcan.wr.usgs.gov/LivingWith/VolcanicPast/Notes/serpentine.html "CVO Website - Serpentine and serpentinite"] {{webarchive|url=https://web.archive.org/web/20111019015059/http://vulcan.wr.usgs.gov/LivingWith/VolcanicPast/Notes/serpentine.html |date=19 October 2011 }}, ''USGS/NPS Geology in the Parks Website'', September 2001, accessed 27 February 2011.</ref> Some species of plants, such as ''[[Clarkia franciscana]]'' and certain species of [[manzanita]], are adapted to living on serpentinite outcrops. However, because serpentinite outcrops are few and isolated, their plant communities are [[ecological island]]s and these distinctive species are often highly endangered.<ref name="Presidio">{{cite web |title=Serpentinite |url=https://www.nps.gov/prsf/learn/nature/serpentinite.htm |access-date=3 September 2021 |website=Presidio of San Francisco |publisher=National Park Service}}</ref> On the other hand, plant communities adapted to living on the serpentine outcrops of [[New Caledonia]] resist displacement by [[introduced species]] that are poorly adapted to this environment.<ref name="futura1">{{cite web|url=http://www.futura-sciences.com/fr/doc/t/zoologie-1/r/nouvelle-caledonie/d/la-faune-et-la-flore-de-nouvelle-caledonie_468/c3/221/p2/ |title=La flore de Nouvelle-Calédonie – Première partie |website=Futura-sciences.com |date=2004-08-18 |access-date=2013-01-30}}</ref>


Serpentine soils are widely distributed on Earth, in part mirroring the distribution of [[ophiolite]]s. There are outcroppings of serpentine soils in the Balkan Peninsula, Turkey, the island of [[Cyprus]], the Alps, Cuba, and New Caledonia. In North America, serpentine soils also are present in small but widely distributed areas on the eastern slope of the [[Appalachian Mountains]] in the eastern United States, and in the Pacific Ranges of Oregon and California.{{citation needed|date=July 2022}}
Serpentine soils are widely distributed on Earth, in part mirroring the distribution of [[ophiolite]]s and other serpentine bearing rocks. <ref>{{Cite web |url=https://academic.oup.com/book/41004/chapter-abstract/349244500?redirectedFrom=fulltext |access-date=2022-11-20 |website=academic.oup.com}}</ref> There are outcroppings of serpentine soils in the Balkan Peninsula, Turkey, the island of [[Cyprus]], the Alps, Cuba, and New Caledonia. In North America, serpentine soils also are present in small but widely distributed areas on the eastern slope of the [[Appalachian Mountains]] in the eastern United States, and in the Pacific Ranges of Oregon and California.{{citation needed|date=July 2022}}

== Occurrences ==
Notable occurrences of serpentinite are found at [[Thetford Mines]], [[Quebec]]; [[Lake Valhalla]], [[New Jersey]]; [[Gila County, Arizona]]; [[Lizard complex]], Lizard Point, Cornwall; and in localities in Greece, Italy, and other parts of Europe.<ref>{{cite book |last1=Sinkankas |first1=John |title=Mineralogy for amateurs. |date=1964 |publisher=Van Nostrand |isbn=0442276249 |location=Princeton, N.J. |pages=149–480}}</ref> Notable ophiolites containing serpentinite include the [[Semail Ophiolite]] of Oman, the [[Troodos Ophiolite]] of [[Cyprus]], the [[Newfoundland]] ophiolites, and the Main Ophiolite Belt of [[New Guinea]].{{sfn|Philpotts|Ague|2009|p=371}}


==Uses==
==Uses==
Line 174: Line 79:


{{Authority control}}
{{Authority control}}

[[Category:Serpentine group]]
[[Category:Metamorphic petrology]]
[[Category:Metamorphic rocks]]

Revision as of 18:24, 22 November 2022

Serpentinite from the Maurienne valley, Savoie, French Alps
Sample of serpentinite from the Golden Gate National Recreation Area, California, United States
Chromitic serpentinite (7.9 cm (3.1 in) across), Styria Province, Austria. Protolith was a Proterozoic-Early Paleozoic upper mantle dunite peridotite that has been multiply metamorphosed during the Devonian, Permian, and Mesozoic.
Tightly folded serpentinite from the Tux Alps, Austria. Closeup view about 30 cm × 20 cm (11.8 in × 7.9 in).

Serpentinite is a rock composed predominantly of one or more serpentine group minerals, the name originating from the similarity of the texture of the rock to that of the skin of a snake.[1] Serpentinite has been called serpentine or serpentine rock, particularly in older geological texts and in wider cultural settings.[2][3][4][5][6]

Formation and mineralogy

Serpentinite is formed by near to complete serpentinization of mafic to ultramafic rocks.[7] Serpentinite can be formed wherever ultramafic rock is infiltrated by water poor in carbon dioxide.[8] This occurs at mid-ocean ridges and in the forearc mantle of subduction zones.[9][10]


The final mineral composition of serpentinite is usually dominated by lizardite, chrysotile, and magnetite. Brucite and antigorite are less commonly present. Lizardite, chrysotile, and antigorite all have approximately the formula Mg3(Si2O5)(OH)4 or (Mg2+, Fe2+)3Si2O5(OH)4, but differ in minor components and in form.[9] Accessory minerals, present in small quantities, include awaruite, other native metal minerals, and sulfide minerals.[11]

Ophiolite of the Gros Morne National Park, Newfoundland. Ophiolites characteristically have a serpentinite component.

Hydrothermal vents and mud volcanoes

A white carbonate spire in the Lost City vent field

Deep sea hydrothermal vents located on serpentinite close to the axis of mid-ocean ridges generally resemble black smokers located on basalt, but emit complex hydrocarbon molecules. The Rainbow field of the Mid-Atlantic Ridge is an example of such hydrothermal vents. Serpentinization alone cannot provide the heat supply for these vents, which must be driven mostly by magmatism. However, the Lost City Hydrothermal Field, located off the axis of the Mid-Atlantic Ridge, may be driven solely by heat of serpentinization. Its vents are unlike black smokers, emitting relatively cool fluids (40 to 75 °C (104 to 167 °F)) that are highly alkaline, high in magnesium, and low in hydrogen sulfide. The vents build up very large chimneys, up to 60 meters (200 ft) in height, composed of carbonate minerals and brucite. Lush microbial communities are associated with the vents. Though the vents themselves are not composed of serpentinite, they are hosted in serpentinite estimated to have formed at a temperature of about 200 °C (392 °F).[12] Sepiolite deposits on mid-ocean ridges may have formed through serpentinite-driven hydrothermal activity.[13] However, geologists continue to debate whether serpentinization alone can account for the heat flux from the Lost City field.[12]

The forearc of the Marianas subduction zone hosts large serpentinite mud volcanoes, which erupt serpentinite mud that rises through faults from the underlying serpentinized forearc mantle. Study of these mud volcanoes gives insights into subduction processes, and the high pH fluids emitted at the volcanoes support a microbial community.[14][10]

Serpentinite thermal vents are a candidate for the environment in which life on Earth originated.[14] Most of the chemical reactions necessary to synthesize acetyl-CoA, essential to basic biochemical pathways of life, take place during serpentinization.[15] The sulfide-metal clusters that activate many enzymes resemble sulfide minerals formed during serpentinization.[16]

Experimental drilling into the gabbro layer of oceanic crust near mid-ocean ridges has demonstrated the presence of a sparse population of hydrocarbon-degrading bacteria. These may feed on hydrocarbons produced by serpentinization of the underlying ultramafic rock.[17][18]

Ecology

Serpentinite ecosystem in the south of New Caledonia
Main article: Serpentine soil

Soil cover over serpentinite bedrock tends to be thin or absent. Soil with serpentine is poor in calcium and other major plant nutrients, but rich in elements toxic to plants such as chromium and nickel.[19] Some species of plants, such as Clarkia franciscana and certain species of manzanita, are adapted to living on serpentinite outcrops. However, because serpentinite outcrops are few and isolated, their plant communities are ecological islands and these distinctive species are often highly endangered.[20] On the other hand, plant communities adapted to living on the serpentine outcrops of New Caledonia resist displacement by introduced species that are poorly adapted to this environment.[21]

Serpentine soils are widely distributed on Earth, in part mirroring the distribution of ophiolites and other serpentine bearing rocks. [22] There are outcroppings of serpentine soils in the Balkan Peninsula, Turkey, the island of Cyprus, the Alps, Cuba, and New Caledonia. In North America, serpentine soils also are present in small but widely distributed areas on the eastern slope of the Appalachian Mountains in the eastern United States, and in the Pacific Ranges of Oregon and California.[citation needed]

Occurrences

Notable occurrences of serpentinite are found at Thetford Mines, Quebec; Lake Valhalla, New Jersey; Gila County, Arizona; Lizard complex, Lizard Point, Cornwall; and in localities in Greece, Italy, and other parts of Europe.[23] Notable ophiolites containing serpentinite include the Semail Ophiolite of Oman, the Troodos Ophiolite of Cyprus, the Newfoundland ophiolites, and the Main Ophiolite Belt of New Guinea.[24]

Uses

Decorative stone in architecture and art

Drinking cups, evidences of serpentinite turning in Zöblitz

Serpentine group minerals have a Mohs hardness of 2.5 to 3.5, so serpentinite is easily carved.[25] Grades of serpentinite higher in calcite, along with the verd antique (breccia form of serpentinite), have historically been used as decorative stones for their marble-like qualities. College Hall at the University of Pennsylvania, for example, is constructed out of serpentine. Popular sources in Europe before contact with the Americas were the mountainous Piedmont region of Italy and Larissa, Greece.[26] Serpentinites are used in many ways in the arts and crafts. For example, the rock has been turned in Zöblitz in Saxony for several hundred years.[27]

Carving stone tools, oil lamp-known as the Qulliq and Inuit sculpture

The Inuit and other indigenous people of the Arctic areas and less so of southern areas used the carved bowl shaped serpentinite qulliq or kudlik lamp with wick, to burn oil or fat to heat, make light and cook with. The Inuit made tools and more recently carvings of animals for commerce.[28]

  • Magnetic serpentine walrus
    Magnetic serpentine walrus
  • Inuit Elder tending the Qulliq, a ceremonial oil lamp made of serpentinite.
    Inuit Elder tending the Qulliq, a ceremonial oil lamp made of serpentinite.

Swiss ovenstone

A variety of chlorite talc schist associated with Alpine serpentinite is found in Val d'Anniviers, Switzerland and was used for making "ovenstones" (Template:Lang-de), a carved stone base beneath a cast iron stove.[29]

Neutron shield in nuclear reactors

Serpentinite has a significant amount of bound water, hence it contains abundant hydrogen atoms able to slow down neutrons by elastic collision (neutron thermalization process). Because of this serpentinite can be used as dry filler inside steel jackets in some designs of nuclear reactors. For example, in RBMK series, as at Chernobyl, it was used for top radiation shielding to protect operators from escaping neutrons.[30] Serpentine can also be added as aggregate to special concrete used in nuclear reactor shielding to increase the concrete density (2.6 g/cm3 (0.094 lb/cu in)) and its neutron capture cross section.[31][32]

CO2 sequestration

Because it readily absorbs carbon dioxide, serpentinite may be of use for sequestering atmospheric carbon dioxide.[33] To speed the reaction, the serpentinite may be reacted with carbon dioxide at elevated temperature in carbonation reactors. Carbon dioxide may also be reacted with alkaline mine waste from serpentine deposits, or carbon dioxide may be injected directly into underground serpentinite formations.[34] Serpentinite may also be used as a source of magnesium in conjunction with electrolytic cells for CO2 scrubbing.[35]

Cultural references

It is the state rock of California, USA and the California Legislature specified that serpentine was "the official State Rock and lithologic emblem."[3] In 2010, a bill was introduced which would have removed serpentine's special status as state rock due to it potentially containing chrysotile asbestos.[36] The bill met with resistance from some California geologists, who noted that the chrysotile present is not hazardous unless it is mobilized in the air as dust.[37] [needs update]

See also

References

  1. ^ Schoenherr, Allan A. (11 July 2017). A Natural History of California: Second Edition. Univ of California Press. pp. 35–. ISBN 9780520295117. Retrieved 6 May 2017.
  2. ^ "serpentine". Merriam-Webster.com Dictionary. Merriam-Webster. Retrieved 6 March 2022.
  3. ^ a b California Government Code § 425.2; see "CA Codes (Gov:420-429.8)". Archived from the original on 28 June 2009. Retrieved 24 December 2009.
  4. ^ Oakeshott, G.B. (1968). "Diapiric Structures in Diablo Range, California". AAPG Special Volume M8:Diapirism and Diapirs. 153: 228–243.
  5. ^ Flett, J.S. (1913). "The geology of the lizard". Proceedings of the Geologists' Association. 24 (3): 118–133. doi:10.1016/S0016-7878(13)80008-9.
  6. ^ González-Mancera, G.; Ortega-Gutiérrez, F.; Nava, N.E.; Arriola, H.S. (2003). "Mössbauer Study of Serpentine Minerals in the Ultramafic Body of Tehuitzingo, Southern Mexico". Hyperfine Interactions. 148 (1–4): 61–71. Bibcode:2003HyInt.148...61G. doi:10.1023/B:HYPE.0000003765.32151.3b. S2CID 96761317.
  7. ^ "Introduction to Mineralogy and Petrology". ScienceDirect. Retrieved 20 November 2022.
  8. ^ Moody 1976, p. 136.
  9. ^ a b Roberts, B. A.; Proctor, J. (6 December 2012). The Ecology of Areas with Serpentinized Rocks: A World View. Springer Science & Business Media. p. 8. ISBN 978-94-011-3722-5.
  10. ^ a b Albers, Elmar; Bach, Wolfgang; Pérez-Gussinyé, Marta; McCammon, Catherine; Frederichs, Thomas (2021). "Serpentinization-Driven H2 Production From Continental Break-Up to Mid-Ocean Ridge Spreading: Unexpected High Rates at the West Iberia Margin". Frontiers in Earth Science. 9. doi:10.3389/feart.2021.673063/full. ISSN 2296-6463.{{cite journal}}: CS1 maint: unflagged free DOI (link)
  11. ^ Moody, Judith B. (April 1976). "Serpentinization: a review". Lithos. 9 (2): 125–138. Bibcode:1976Litho...9..125M. doi:10.1016/0024-4937(76)90030-X.
  12. ^ a b Allen, Douglas E.; Seyfried, W.E. (March 2004). "Serpentinization and heat generation: constraints from Lost City and Rainbow hydrothermal systems 1 1Associate editor: J. C. Alt". Geochimica et Cosmochimica Acta. 68 (6): 1347–1354. doi:10.1016/j.gca.2003.09.003.
  13. ^ Mével, Catherine (September 2003). "Serpentinization of abyssal peridotites at mid-ocean ridges". Comptes Rendus Geoscience. 335 (10–11): 825–852. Bibcode:2003CRGeo.335..825M. doi:10.1016/j.crte.2003.08.006.
  14. ^ a b Fryer, Patricia (15 January 2012). "Serpentinite Mud Volcanism: Observations, Processes, and Implications". Annual Review of Marine Science. 4 (1): 345–373. Bibcode:2012ARMS....4..345F. doi:10.1146/annurev-marine-120710-100922. ISSN 1941-1405. PMID 22457979.
  15. ^ Martin, William; Russell, Michael J (29 October 2007). "On the origin of biochemistry at an alkaline hydrothermal vent". Philosophical Transactions of the Royal Society B: Biological Sciences. 362 (1486): 1887–1926. doi:10.1098/rstb.2006.1881. PMC 2442388. PMID 17255002.
  16. ^ McCollom, T. M.; Seewald, J. S. (1 April 2013). "Serpentinites, Hydrogen, and Life". Elements. 9 (2): 129–134. CiteSeerX 10.1.1.852.2089. doi:10.2113/gselements.9.2.129. Retrieved 5 September 2021.
  17. ^ Mason, Olivia U.; Nakagawa, Tatsunori; Rosner, Martin; Van Nostrand, Joy D.; Zhou, Jizhong; Maruyama, Akihiko; Fisk, Martin R.; Giovannoni, Stephen J. (5 November 2010). "First Investigation of the Microbiology of the Deepest Layer of Ocean Crust". PLOS ONE. 5 (11): e15399. Bibcode:2010PLoSO...515399M. doi:10.1371/journal.pone.0015399. PMC 2974637. PMID 21079766.
  18. ^ Marshall, Michael (17 November 2010). "Life is found in deepest layer of Earth's crust". New Scientist. Retrieved 3 December 2021.
  19. ^ "CVO Website - Serpentine and serpentinite" Archived 19 October 2011 at the Wayback Machine, USGS/NPS Geology in the Parks Website, September 2001, accessed 27 February 2011.
  20. ^ "Serpentinite". Presidio of San Francisco. National Park Service. Retrieved 3 September 2021.
  21. ^ "La flore de Nouvelle-Calédonie – Première partie". Futura-sciences.com. 18 August 2004. Retrieved 30 January 2013.
  22. ^ academic.oup.com https://academic.oup.com/book/41004/chapter-abstract/349244500?redirectedFrom=fulltext. Retrieved 20 November 2022. {{cite web}}: Missing or empty |title= (help)
  23. ^ Sinkankas, John (1964). Mineralogy for amateurs. Princeton, N.J.: Van Nostrand. pp. 149–480. ISBN 0442276249.
  24. ^ Philpotts & Ague 2009, p. 371.
  25. ^ Nesse, William D. (2000). Introduction to mineralogy. New York: Oxford University Press. p. 239. ISBN 9780195106916.
  26. ^ Ashurst, John. Dimes, Francis G. Conservation of building and decorative stone. Elsevier Butterworth-Heinemann, 1990, p. 51.
  27. ^ Eva Maria Hoyer: Sächsischer Serpentin: ein Stein und seine Verwendung. Edition Leipzig, Leipzig 1996, pp. 20–22.
  28. ^ Kerr, A.; Squires, G.C. "Serpentinites and associated rock types near Hopedale, Nunatsiavut: Potential for artisanal carving-stone resources" (PDF). Geological Survey Report. 19 (1). Newfoundland and Labrador Department of Natural Resources: 39–57. Retrieved 3 September 2021.
  29. ^ Talcose-schist from Canton Valais. By Thomags Bonney, (Geol. Mag., 1897, N.S., [iv], 4, 110--116) abstract
  30. ^ Lithuanian Energy Institute (28 May 2011). "Design of structures, components, equipments and systems". Ignalina Source Book. Archived from the original on 9 October 2011. Retrieved 28 May 2011.
  31. ^ Aminian, A.; Nematollahi, M.R.; Haddad, K.; Mehdizadeh, S. (3–8 June 2007). Determination of shielding parameters for different types of concretes by Monte Carlo methods (PDF). ICENES 2007: International Conference on Emerging Nuclear Energy Systems. Session 12B: Radiation effects. Istanbul, Turkey. p. 7. Archived from the original (PDF) on 3 March 2016. Retrieved 28 May 2011.
  32. ^ Abulfaraj, Waleed H.; Salah M. Kamal (1994). "Evaluation of ilmenite serpentine concrete and ordinary concrete as nuclear reactor shielding". Radiation Physics and Chemistry. 44 (1–2): 139–148. Bibcode:1994RaPC...44..139A. doi:10.1016/0969-806X(94)90120-1. ISSN 0969-806X.
  33. ^ Farhang, F.; Oliver, T.K.; Rayson, M.S.; Brent, G.F.; Molloy, T.S.; Stockenhuber, M.; Kennedy, E.M. (March 2019). "Dissolution of heat activated serpentine for CO2 sequestration: The effect of silica precipitation at different temperature and pH values". Journal of CO2 Utilization. 30: 123–129. doi:10.1016/j.jcou.2019.01.009. S2CID 104424416.
  34. ^ Power, I. M.; Wilson, S. A.; Dipple, G. M. (1 April 2013). "Serpentinite Carbonation for CO2 Sequestration". Elements. 9 (2): 115–121. doi:10.2113/gselements.9.2.115.
  35. ^ Li, Wenzhi; Li, Wen; Li, Baoqing; Bai, Zongqing (February 2009). "Electrolysis and heat pretreatment methods to promote CO2 sequestration by mineral carbonation". Chemical Engineering Research and Design. 87 (2): 210–215. doi:10.1016/j.cherd.2008.08.001.
  36. ^ Fimrite, Peter (16 July 2010). "Geologists protest bill to remove state rock". San Francisco Chronicle. Retrieved 17 April 2018.
  37. ^ Frazell, Julie; Elkins, Rachel; O'Geen, Anthony; Reynolds, Robert; Meyers, James. "Facts about Serpentine Rock and Soil Containing Asbestos in California" (PDF). ANR Catalog. University of California Division of Agriculture and Natural Resources. Retrieved 17 April 2018.
Wikimedia Commons has media related to Serpentinite.
Retrieved from "https://en.wikipedia.org/enwiki/w/index.php?title=Serpentinite&oldid=1123231706"