Fe–Ni–Co–O–S Phase Relations in Peridotite–Seawater Interactions
Identifieur interne : 000637 ( Istex/Corpus ); précédent : 000636; suivant : 000638Fe–Ni–Co–O–S Phase Relations in Peridotite–Seawater Interactions
Auteurs : Frieder Klein ; Wolfgang BachSource :
- Journal of Petrology [ 0022-3530 ] ; 2009-01.
Abstract
Serpentinization of abyssal peridotites is known to produce extremely reducing conditions as a result of dihydrogen (H2,aq) release upon oxidation of ferrous iron in primary phases to ferric iron in secondary minerals by H2O. We have compiled and evaluated thermodynamic data for Fe–Ni–Co–O–S phases and computed phase relations in fO2,g–fS2,g and aH2,aq–aH2S,aq diagrams for temperatures between 150 and 400°C at 50 MPa. We use the relations and compositions of Fe–Ni–Co–O–S phases to trace changes in oxygen and sulfur fugacities during progressive serpentinization and steatitization of peridotites from the Mid-Atlantic Ridge in the 15°20′N Fracture Zone area (Ocean Drilling Program Leg 209). Petrographic observations suggest a systematic change from awaruite–magnetite–pentlandite and heazlewoodite–magnetite–pentlandite assemblages forming in the early stages of serpentinization to millerite–pyrite–polydymite-dominated assemblages in steatized rocks. Awaruite is observed in all brucite-bearing partly serpentinized rocks. Apparently, buffering of silica activities to low values by the presence of brucite facilitates the formation of large amounts of hydrogen, which leads to the formation of awaruite. Associated with the prominent desulfurization of pentlandite, sulfide is removed from the rock during the initial stage of serpentinization. In contrast, steatitization indicates increased silica activities and that high-sulfur-fugacity sulfides, such as polydymite and pyrite–vaesite solid solution, form as the reducing capacity of the peridotite is exhausted and H2 activities drop. Under these conditions, sulfides will not desulfurize but precipitate and the sulfur content of the rock increases. The co-evolution of fO2,g–fS2,g in the system follows an isopotential of H2S,aq, indicating that H2S in vent fluids is buffered. In contrast, H2 in vent fluids is not buffered by Fe–Ni–Co–O–S phases, which merely monitor the evolution of H2 activities in the fluids in the course of progressive rock alteration. The co-occurrence of pentlandite–awaruite–magnetite indicates H2,aq activities in the interacting fluids near the stability limit of water. The presence of a hydrogen gas phase would add to the catalyzing capacity of awaruite and would facilitate the abiotic formation of organic compounds.
Url:
DOI: 10.1093/petrology/egn071
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<record><TEI wicri:istexFullTextTei="biblStruct"><teiHeader><fileDesc><titleStmt><title>Fe–Ni–Co–O–S Phase Relations in Peridotite–Seawater Interactions</title><author><name sortKey="Klein, Frieder" sort="Klein, Frieder" uniqKey="Klein F" first="Frieder" last="Klein">Frieder Klein</name><affiliation><mods:affiliation>Geoscience Department, University of Bremen, Klagenfurter Straße, 28359 Bremen, Germany</mods:affiliation></affiliation></author><author><name sortKey="Bach, Wolfgang" sort="Bach, Wolfgang" uniqKey="Bach W" first="Wolfgang" last="Bach">Wolfgang Bach</name><affiliation><mods:affiliation>E-mail: wbach@uni-bremen.de</mods:affiliation></affiliation></author></titleStmt><publicationStmt><idno type="wicri:source">ISTEX</idno><idno type="RBID">ISTEX:F97A415FEAB79FB0B24DE8825DDBEBCD1E8C538F</idno><date when="2009" year="2009">2009</date><idno type="doi">10.1093/petrology/egn071</idno><idno type="url">https://api.istex.fr/document/F97A415FEAB79FB0B24DE8825DDBEBCD1E8C538F/fulltext/pdf</idno><idno type="wicri:Area/Istex/Corpus">000637</idno><idno type="wicri:explorRef" wicri:stream="Istex" wicri:step="Corpus" wicri:corpus="ISTEX">000637</idno></publicationStmt><sourceDesc><biblStruct><analytic><title level="a">Fe–Ni–Co–O–S Phase Relations in Peridotite–Seawater Interactions</title><author><name sortKey="Klein, Frieder" sort="Klein, Frieder" uniqKey="Klein F" first="Frieder" last="Klein">Frieder Klein</name><affiliation><mods:affiliation>Geoscience Department, University of Bremen, Klagenfurter Straße, 28359 Bremen, Germany</mods:affiliation></affiliation></author><author><name sortKey="Bach, Wolfgang" sort="Bach, Wolfgang" uniqKey="Bach W" first="Wolfgang" last="Bach">Wolfgang Bach</name><affiliation><mods:affiliation>E-mail: wbach@uni-bremen.de</mods:affiliation></affiliation></author></analytic><monogr></monogr><series><title level="j">Journal of Petrology</title><idno type="ISSN">0022-3530</idno><idno type="eISSN">1460-2415</idno><imprint><publisher>Oxford University Press</publisher><date type="published" when="2009-01">2009-01</date><biblScope unit="volume">50</biblScope><biblScope unit="issue">1</biblScope><biblScope unit="page" from="37">37</biblScope><biblScope unit="page" to="59">59</biblScope></imprint><idno type="ISSN">0022-3530</idno></series><idno type="istex">F97A415FEAB79FB0B24DE8825DDBEBCD1E8C538F</idno><idno type="DOI">10.1093/petrology/egn071</idno><idno type="ArticleID">egn071</idno></biblStruct></sourceDesc><seriesStmt><idno type="ISSN">0022-3530</idno></seriesStmt></fileDesc><profileDesc><textClass></textClass><langUsage><language ident="en">en</language></langUsage></profileDesc></teiHeader><front><div type="abstract">Serpentinization of abyssal peridotites is known to produce extremely reducing conditions as a result of dihydrogen (H2,aq) release upon oxidation of ferrous iron in primary phases to ferric iron in secondary minerals by H2O. We have compiled and evaluated thermodynamic data for Fe–Ni–Co–O–S phases and computed phase relations in fO2,g–fS2,g and aH2,aq–aH2S,aq diagrams for temperatures between 150 and 400°C at 50 MPa. We use the relations and compositions of Fe–Ni–Co–O–S phases to trace changes in oxygen and sulfur fugacities during progressive serpentinization and steatitization of peridotites from the Mid-Atlantic Ridge in the 15°20′N Fracture Zone area (Ocean Drilling Program Leg 209). Petrographic observations suggest a systematic change from awaruite–magnetite–pentlandite and heazlewoodite–magnetite–pentlandite assemblages forming in the early stages of serpentinization to millerite–pyrite–polydymite-dominated assemblages in steatized rocks. Awaruite is observed in all brucite-bearing partly serpentinized rocks. Apparently, buffering of silica activities to low values by the presence of brucite facilitates the formation of large amounts of hydrogen, which leads to the formation of awaruite. Associated with the prominent desulfurization of pentlandite, sulfide is removed from the rock during the initial stage of serpentinization. In contrast, steatitization indicates increased silica activities and that high-sulfur-fugacity sulfides, such as polydymite and pyrite–vaesite solid solution, form as the reducing capacity of the peridotite is exhausted and H2 activities drop. Under these conditions, sulfides will not desulfurize but precipitate and the sulfur content of the rock increases. The co-evolution of fO2,g–fS2,g in the system follows an isopotential of H2S,aq, indicating that H2S in vent fluids is buffered. In contrast, H2 in vent fluids is not buffered by Fe–Ni–Co–O–S phases, which merely monitor the evolution of H2 activities in the fluids in the course of progressive rock alteration. The co-occurrence of pentlandite–awaruite–magnetite indicates H2,aq activities in the interacting fluids near the stability limit of water. The presence of a hydrogen gas phase would add to the catalyzing capacity of awaruite and would facilitate the abiotic formation of organic compounds.</div></front></TEI><istex><corpusName>oup</corpusName><author><json:item><name>Frieder Klein</name><affiliations><json:string>Geoscience Department, University of Bremen, Klagenfurter Straße, 28359 Bremen, Germany</json:string></affiliations></json:item><json:item><name>Wolfgang Bach</name><affiliations><json:string>E-mail: wbach@uni-bremen.de</json:string></affiliations></json:item></author><subject><json:item><lang><json:string>eng</json:string></lang><value>Original Papers</value></json:item><json:item><lang><json:string>eng</json:string></lang><value>serpentinization</value></json:item><json:item><lang><json:string>eng</json:string></lang><value>ODP Expedition 209</value></json:item><json:item><lang><json:string>eng</json:string></lang><value>sulfide</value></json:item><json:item><lang><json:string>eng</json:string></lang><value>oxygen fugacity</value></json:item><json:item><lang><json:string>eng</json:string></lang><value>sulfur fugacity</value></json:item><json:item><lang><json:string>eng</json:string></lang><value>hydrothermal system</value></json:item><json:item><lang><json:string>eng</json:string></lang><value>metasomatism</value></json:item><json:item><lang><json:string>eng</json:string></lang><value>Mid-Atlantic Ridge</value></json:item></subject><articleId><json:string>egn071</json:string></articleId><language><json:string>eng</json:string></language><originalGenre><json:string>research-article</json:string></originalGenre><abstract>Serpentinization of abyssal peridotites is known to produce extremely reducing conditions as a result of dihydrogen (H2,aq) release upon oxidation of ferrous iron in primary phases to ferric iron in secondary minerals by H2O. We have compiled and evaluated thermodynamic data for Fe–Ni–Co–O–S phases and computed phase relations in fO2,g–fS2,g and aH2,aq–aH2S,aq diagrams for temperatures between 150 and 400°C at 50 MPa. We use the relations and compositions of Fe–Ni–Co–O–S phases to trace changes in oxygen and sulfur fugacities during progressive serpentinization and steatitization of peridotites from the Mid-Atlantic Ridge in the 15°20′N Fracture Zone area (Ocean Drilling Program Leg 209). Petrographic observations suggest a systematic change from awaruite–magnetite–pentlandite and heazlewoodite–magnetite–pentlandite assemblages forming in the early stages of serpentinization to millerite–pyrite–polydymite-dominated assemblages in steatized rocks. Awaruite is observed in all brucite-bearing partly serpentinized rocks. Apparently, buffering of silica activities to low values by the presence of brucite facilitates the formation of large amounts of hydrogen, which leads to the formation of awaruite. Associated with the prominent desulfurization of pentlandite, sulfide is removed from the rock during the initial stage of serpentinization. In contrast, steatitization indicates increased silica activities and that high-sulfur-fugacity sulfides, such as polydymite and pyrite–vaesite solid solution, form as the reducing capacity of the peridotite is exhausted and H2 activities drop. Under these conditions, sulfides will not desulfurize but precipitate and the sulfur content of the rock increases. The co-evolution of fO2,g–fS2,g in the system follows an isopotential of H2S,aq, indicating that H2S in vent fluids is buffered. In contrast, H2 in vent fluids is not buffered by Fe–Ni–Co–O–S phases, which merely monitor the evolution of H2 activities in the fluids in the course of progressive rock alteration. The co-occurrence of pentlandite–awaruite–magnetite indicates H2,aq activities in the interacting fluids near the stability limit of water. 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Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oxfordjournals.org</p></availability><date>2009-02-12</date></publicationStmt><sourceDesc><biblStruct type="inbook"><analytic><title level="a">Fe–Ni–Co–O–S Phase Relations in Peridotite–Seawater Interactions</title><author xml:id="author-1"><persName><forename type="first">Frieder</forename><surname>Klein</surname></persName><affiliation>Geoscience Department, University of Bremen, Klagenfurter Straße, 28359 Bremen, Germany</affiliation></author><author xml:id="author-2" corresp="yes"><persName><forename type="first">Wolfgang</forename><surname>Bach</surname></persName><email>wbach@uni-bremen.de</email></author></analytic><monogr><title level="j">Journal of Petrology</title><idno type="pISSN">0022-3530</idno><idno type="eISSN">1460-2415</idno><imprint><publisher>Oxford University Press</publisher><date type="published" when="2009-01"></date><biblScope unit="volume">50</biblScope><biblScope unit="issue">1</biblScope><biblScope unit="page" from="37">37</biblScope><biblScope unit="page" to="59">59</biblScope></imprint></monogr><idno type="istex">F97A415FEAB79FB0B24DE8825DDBEBCD1E8C538F</idno><idno type="DOI">10.1093/petrology/egn071</idno><idno type="ArticleID">egn071</idno></biblStruct></sourceDesc></fileDesc><profileDesc><creation><date>2009-02-12</date></creation><langUsage><language ident="en">en</language></langUsage><abstract><p>Serpentinization of abyssal peridotites is known to produce extremely reducing conditions as a result of dihydrogen (H2,aq) release upon oxidation of ferrous iron in primary phases to ferric iron in secondary minerals by H2O. We have compiled and evaluated thermodynamic data for Fe–Ni–Co–O–S phases and computed phase relations in fO2,g–fS2,g and aH2,aq–aH2S,aq diagrams for temperatures between 150 and 400°C at 50 MPa. We use the relations and compositions of Fe–Ni–Co–O–S phases to trace changes in oxygen and sulfur fugacities during progressive serpentinization and steatitization of peridotites from the Mid-Atlantic Ridge in the 15°20′N Fracture Zone area (Ocean Drilling Program Leg 209). Petrographic observations suggest a systematic change from awaruite–magnetite–pentlandite and heazlewoodite–magnetite–pentlandite assemblages forming in the early stages of serpentinization to millerite–pyrite–polydymite-dominated assemblages in steatized rocks. Awaruite is observed in all brucite-bearing partly serpentinized rocks. Apparently, buffering of silica activities to low values by the presence of brucite facilitates the formation of large amounts of hydrogen, which leads to the formation of awaruite. Associated with the prominent desulfurization of pentlandite, sulfide is removed from the rock during the initial stage of serpentinization. In contrast, steatitization indicates increased silica activities and that high-sulfur-fugacity sulfides, such as polydymite and pyrite–vaesite solid solution, form as the reducing capacity of the peridotite is exhausted and H2 activities drop. Under these conditions, sulfides will not desulfurize but precipitate and the sulfur content of the rock increases. The co-evolution of fO2,g–fS2,g in the system follows an isopotential of H2S,aq, indicating that H2S in vent fluids is buffered. In contrast, H2 in vent fluids is not buffered by Fe–Ni–Co–O–S phases, which merely monitor the evolution of H2 activities in the fluids in the course of progressive rock alteration. The co-occurrence of pentlandite–awaruite–magnetite indicates H2,aq activities in the interacting fluids near the stability limit of water. The presence of a hydrogen gas phase would add to the catalyzing capacity of awaruite and would facilitate the abiotic formation of organic compounds.</p></abstract><textClass><keywords scheme="keyword"><list><item><term>Original Papers</term></item></list></keywords></textClass><textClass><keywords scheme="keyword"><list><head>keywords</head><item><term>serpentinization</term></item><item><term>ODP Expedition 209</term></item><item><term>sulfide</term></item><item><term>oxygen fugacity</term></item><item><term>sulfur fugacity</term></item><item><term>hydrothermal system</term></item><item><term>metasomatism</term></item><item><term>Mid-Atlantic Ridge</term></item></list></keywords></textClass></profileDesc><revisionDesc><change when="2009-02-12">Created</change><change when="2009-01">Published</change><change xml:id="refBibs-istex" who="#ISTEX-API" when="2016-10-14">References added</change></revisionDesc></teiHeader></istex:fulltextTEI><json:item><original>false</original><mimetype>text/plain</mimetype><extension>txt</extension><uri>https://api.istex.fr/document/F97A415FEAB79FB0B24DE8825DDBEBCD1E8C538F/fulltext/txt</uri></json:item></fulltext><metadata><istex:metadataXml wicri:clean="corpus oup" wicri:toSee="no header"><istex:xmlDeclaration>version="1.0" encoding="utf-8"</istex:xmlDeclaration><istex:docType PUBLIC="-//NLM//DTD Journal Publishing DTD v2.3 20070202//EN" URI="journalpublishing.dtd" name="istex:docType"></istex:docType><istex:document><article article-type="research-article"><front><journal-meta><journal-id journal-id-type="hwp">petrology</journal-id><journal-id journal-id-type="publisher-id">petroj</journal-id><journal-title>Journal of Petrology</journal-title><issn pub-type="ppub">0022-3530</issn><issn pub-type="epub">1460-2415</issn><publisher><publisher-name>Oxford University Press</publisher-name></publisher></journal-meta><article-meta><article-id pub-id-type="doi">10.1093/petrology/egn071</article-id><article-id pub-id-type="publisher-id">egn071</article-id><article-categories><subj-group><subject>Original Papers</subject></subj-group></article-categories><title-group><article-title>Fe–Ni–Co–O–S Phase Relations in Peridotite–Seawater Interactions</article-title></title-group><contrib-group><contrib contrib-type="author"><name><surname>Klein</surname><given-names>Frieder</given-names></name></contrib><contrib contrib-type="author" corresp="yes"><name><surname>Bach</surname><given-names>Wolfgang</given-names></name><xref ref-type="corresp" rid="COR1">*</xref></contrib></contrib-group><aff>Geoscience Department, University of Bremen, Klagenfurter Straße, 28359 Bremen, Germany</aff><author-notes><corresp id="COR1">*Corresponding author. Telephone: <phone>0049-421-218-65400</phone>. Fax: <fax>0049-421-218-65429</fax>. E-mail: <email>wbach@uni-bremen.de</email></corresp></author-notes><pub-date pub-type="ppub"><month>1</month><year>2009</year></pub-date><pub-date pub-type="epub"><day>12</day><month>2</month><year>2009</year></pub-date><volume>50</volume><issue>1</issue><fpage>37</fpage><lpage>59</lpage><history><date date-type="received"><day>8</day><month>9</month><year>2008</year></date><date date-type="accepted"><day>28</day><month>11</month><year>2008</year></date></history><permissions><copyright-statement>© The Author 2009. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oxfordjournals.org</copyright-statement><copyright-year>2009</copyright-year></permissions><abstract><p>Serpentinization of abyssal peridotites is known to produce extremely reducing conditions as a result of dihydrogen (H<sub>2</sub>,aq) release upon oxidation of ferrous iron in primary phases to ferric iron in secondary minerals by H<sub>2</sub>O. We have compiled and evaluated thermodynamic data for Fe–Ni–Co–O–S phases and computed phase relations in fO<sub>2</sub>,g–fS<sub>2</sub>,g and <italic>a</italic>H<sub>2</sub>,aq–<italic>a</italic>H<sub>2</sub>S,aq diagrams for temperatures between 150 and 400°C at 50 MPa. We use the relations and compositions of Fe–Ni–Co–O–S phases to trace changes in oxygen and sulfur fugacities during progressive serpentinization and steatitization of peridotites from the Mid-Atlantic Ridge in the 15°20′N Fracture Zone area (Ocean Drilling Program Leg 209). Petrographic observations suggest a systematic change from awaruite–magnetite–pentlandite and heazlewoodite–magnetite–pentlandite assemblages forming in the early stages of serpentinization to millerite–pyrite–polydymite-dominated assemblages in steatized rocks. Awaruite is observed in all brucite-bearing partly serpentinized rocks. Apparently, buffering of silica activities to low values by the presence of brucite facilitates the formation of large amounts of hydrogen, which leads to the formation of awaruite. Associated with the prominent desulfurization of pentlandite, sulfide is removed from the rock during the initial stage of serpentinization. In contrast, steatitization indicates increased silica activities and that high-sulfur-fugacity sulfides, such as polydymite and pyrite–vaesite solid solution, form as the reducing capacity of the peridotite is exhausted and H<sub>2</sub> activities drop. Under these conditions, sulfides will not desulfurize but precipitate and the sulfur content of the rock increases. The co-evolution of fO<sub>2</sub>,g–fS<sub>2</sub>,g in the system follows an isopotential of H<sub>2</sub>S,aq, indicating that H<sub>2</sub>S in vent fluids is buffered. In contrast, H<sub>2</sub> in vent fluids is not buffered by Fe–Ni–Co–O–S phases, which merely monitor the evolution of H<sub>2</sub> activities in the fluids in the course of progressive rock alteration. The co-occurrence of pentlandite–awaruite–magnetite indicates H<sub>2</sub>,aq activities in the interacting fluids near the stability limit of water. The presence of a hydrogen gas phase would add to the catalyzing capacity of awaruite and would facilitate the abiotic formation of organic compounds.</p></abstract><kwd-group><kwd>serpentinization</kwd><kwd>ODP Expedition 209</kwd><kwd>sulfide</kwd><kwd>oxygen fugacity</kwd><kwd>sulfur fugacity</kwd><kwd>hydrothermal system</kwd><kwd>metasomatism</kwd><kwd>Mid-Atlantic Ridge</kwd></kwd-group></article-meta></front></article></istex:document></istex:metadataXml><mods version="3.6"><titleInfo><title>Fe–Ni–Co–O–S Phase Relations in Peridotite–Seawater Interactions</title></titleInfo><titleInfo type="alternative" contentType="CDATA"><title>Fe–Ni–Co–O–S Phase Relations in Peridotite–Seawater Interactions</title></titleInfo><name type="personal"><namePart type="given">Frieder</namePart><namePart type="family">Klein</namePart><affiliation>Geoscience Department, University of Bremen, Klagenfurter Straße, 28359 Bremen, Germany</affiliation><role><roleTerm type="text">author</roleTerm></role></name><name type="personal" displayLabel="corresp"><namePart type="given">Wolfgang</namePart><namePart type="family">Bach</namePart><affiliation>E-mail: wbach@uni-bremen.de</affiliation><role><roleTerm type="text">author</roleTerm></role></name><typeOfResource>text</typeOfResource><genre type="research-article" displayLabel="research-article"></genre><subject><topic>Original Papers</topic></subject><originInfo><publisher>Oxford University Press</publisher><dateIssued encoding="w3cdtf">2009-01</dateIssued><dateCreated encoding="w3cdtf">2009-02-12</dateCreated><copyrightDate encoding="w3cdtf">2009</copyrightDate></originInfo><language><languageTerm type="code" authority="iso639-2b">eng</languageTerm><languageTerm type="code" authority="rfc3066">en</languageTerm></language><physicalDescription><internetMediaType>text/html</internetMediaType></physicalDescription><abstract>Serpentinization of abyssal peridotites is known to produce extremely reducing conditions as a result of dihydrogen (H2,aq) release upon oxidation of ferrous iron in primary phases to ferric iron in secondary minerals by H2O. We have compiled and evaluated thermodynamic data for Fe–Ni–Co–O–S phases and computed phase relations in fO2,g–fS2,g and aH2,aq–aH2S,aq diagrams for temperatures between 150 and 400°C at 50 MPa. We use the relations and compositions of Fe–Ni–Co–O–S phases to trace changes in oxygen and sulfur fugacities during progressive serpentinization and steatitization of peridotites from the Mid-Atlantic Ridge in the 15°20′N Fracture Zone area (Ocean Drilling Program Leg 209). Petrographic observations suggest a systematic change from awaruite–magnetite–pentlandite and heazlewoodite–magnetite–pentlandite assemblages forming in the early stages of serpentinization to millerite–pyrite–polydymite-dominated assemblages in steatized rocks. Awaruite is observed in all brucite-bearing partly serpentinized rocks. Apparently, buffering of silica activities to low values by the presence of brucite facilitates the formation of large amounts of hydrogen, which leads to the formation of awaruite. Associated with the prominent desulfurization of pentlandite, sulfide is removed from the rock during the initial stage of serpentinization. In contrast, steatitization indicates increased silica activities and that high-sulfur-fugacity sulfides, such as polydymite and pyrite–vaesite solid solution, form as the reducing capacity of the peridotite is exhausted and H2 activities drop. Under these conditions, sulfides will not desulfurize but precipitate and the sulfur content of the rock increases. The co-evolution of fO2,g–fS2,g in the system follows an isopotential of H2S,aq, indicating that H2S in vent fluids is buffered. In contrast, H2 in vent fluids is not buffered by Fe–Ni–Co–O–S phases, which merely monitor the evolution of H2 activities in the fluids in the course of progressive rock alteration. The co-occurrence of pentlandite–awaruite–magnetite indicates H2,aq activities in the interacting fluids near the stability limit of water. The presence of a hydrogen gas phase would add to the catalyzing capacity of awaruite and would facilitate the abiotic formation of organic compounds.</abstract><subject><genre>keywords</genre><topic>serpentinization</topic><topic>ODP Expedition 209</topic><topic>sulfide</topic><topic>oxygen fugacity</topic><topic>sulfur fugacity</topic><topic>hydrothermal system</topic><topic>metasomatism</topic><topic>Mid-Atlantic Ridge</topic></subject><relatedItem type="host"><titleInfo><title>Journal of Petrology</title></titleInfo><genre type="journal">journal</genre><identifier type="ISSN">0022-3530</identifier><identifier type="eISSN">1460-2415</identifier><identifier type="PublisherID">petroj</identifier><identifier type="PublisherID-hwp">petrology</identifier><part><date>2009</date><detail type="volume"><caption>vol.</caption><number>50</number></detail><detail type="issue"><caption>no.</caption><number>1</number></detail><extent unit="pages"><start>37</start><end>59</end></extent></part></relatedItem><identifier type="istex">F97A415FEAB79FB0B24DE8825DDBEBCD1E8C538F</identifier><identifier type="DOI">10.1093/petrology/egn071</identifier><identifier type="ArticleID">egn071</identifier><accessCondition type="use and reproduction" contentType="copyright">© The Author 2009. 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