Editing Serpentinization (section)

==== Forearc mantle ====
Serpentinization is an important phenomenon in subduction zones that has a strong control on the water cycle and geodynamics of a subduction zone. <ref name=":3">{{Cite journal |last1=Xia |first1=Shaohong |last2=Sun |first2=Jinlong |last3=Huang |first3=Haibo |date=2017-05-31 |title=Degree of serpentinization in the forearc mantle wedge of Kyushu subduction zone |url=http://dx.doi.org/10.1190/igc2017-238 |journal=International Geophysical Conference, Qingdao, China, 17-20 April 2017 |pages=941–943 |publisher=Society of Exploration Geophysicists and Chinese Petroleum Society |doi=10.1190/igc2017-238|url-access=subscription }}</ref> 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.<ref name=":3" /> 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 lowers the density of the original rock, serpentinization may lead to uplift or exhumation of serpentinites to the surface, as has taken place with the serpentinite exposed at the [[Presidio of San Francisco]] following cessation of subduction.<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>
 
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]]''. <ref>{{Cite web |date=2010-04-15 |title=Ophiolites |url=https://volcano.oregonstate.edu/volcanic-minerals/ophiolites |access-date=2022-11-20 |website=Volcano World |language=en}}</ref> 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> 
[[File:Serpentinization Process at Subduction Zone.jpg|thumb|Hydration of [[forearc]] mantle due to the water expelled from deeper part of the subducting plate. Adapted from Hyndman and Peacock (2003)]]