Wetting of mantle olivine by sulfide melt: implications for Re/Os ratios in mantle peridotite and late-stage core formation
Identifieur interne : 001856 ( Istex/Corpus ); précédent : 001855; suivant : 001857Wetting of mantle olivine by sulfide melt: implications for Re/Os ratios in mantle peridotite and late-stage core formation
Auteurs : Glenn A. Gaetani ; Timothy L. GroveSource :
- Earth and Planetary Science Letters [ 0012-821X ] ; 1999.
Abstract
This study investigates the effects of variations in the relative fugacities of oxygen and sulfur on the wetting of mantle olivine by molten sulfide. Experiments were performed on mixtures of San Carlos olivine and synthetic FeS at 1 bar and 1350°C. Crucibles were fabricated from San Carlos olivine, and the fugacities of oxygen and sulfur were controlled by mixing CO2, CO, and SO2 gases. Experimental conditions ranged from logfO2=−7.9 to −10.3 and from logfS2=−1.5 to −2.5. Our experimental results demonstrate that, at a given temperature and pressure, the olivine–sulfide melt dihedral angle is controlled by the concentration of O dissolved in an anion-rich melt. Trace amounts of O dissolve in sulfide melt at fO2 conditions near the iron–wüstite oxygen buffer and the dihedral angle is 90°. At fO2 conditions near the fayalite–magnetite–quartz oxygen buffer the concentration of dissolved O is near 9 wt% and the dihedral angle is 52°, allowing small amounts of sulfide melt to form an interconnected network in olivine-rich rocks and to migrate via porous flow. These results indicate that sulfide melt is likely to be mobile at current upper mantle fO2 and fS2 conditions. In mantle peridotite, the addition or removal of sulfide melt by porous flow will variably fractionate Re/Os, U/Pb, and Th/Pb ratios because Os and Pb are more chalcophile than Re, U, and Th. The Re/Os ratio of the peridotite is especially sensitive to this process. The mobility of sulfide melt at oxidizing conditions implies that the addition of oxidized chondritic material during the later stages of the accretion of the Earth may have facilitated the segregation of core-forming material by porous flow if temperatures were in excess of the sulfide solidus.
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DOI: 10.1016/S0012-821X(99)00062-X
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<record><TEI wicri:istexFullTextTei="biblStruct"><teiHeader><fileDesc><titleStmt><title>Wetting of mantle olivine by sulfide melt: implications for Re/Os ratios in mantle peridotite and late-stage core formation</title><author><name sortKey="Gaetani, Glenn A" sort="Gaetani, Glenn A" uniqKey="Gaetani G" first="Glenn A" last="Gaetani">Glenn A. Gaetani</name><affiliation><mods:affiliation>Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA</mods:affiliation></affiliation></author><author><name sortKey="Grove, Timothy L" sort="Grove, Timothy L" uniqKey="Grove T" first="Timothy L" last="Grove">Timothy L. Grove</name><affiliation><mods:affiliation>Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA</mods:affiliation></affiliation></author></titleStmt><publicationStmt><idno type="wicri:source">ISTEX</idno><idno type="RBID">ISTEX:AFD1BFCF3E007EA4D7BC18803EB8BA4D13C0359F</idno><date when="1999" year="1999">1999</date><idno type="doi">10.1016/S0012-821X(99)00062-X</idno><idno type="url">https://api.istex.fr/document/AFD1BFCF3E007EA4D7BC18803EB8BA4D13C0359F/fulltext/pdf</idno><idno type="wicri:Area/Istex/Corpus">001856</idno><idno type="wicri:explorRef" wicri:stream="Istex" wicri:step="Corpus" wicri:corpus="ISTEX">001856</idno></publicationStmt><sourceDesc><biblStruct><analytic><title level="a">Wetting of mantle olivine by sulfide melt: implications for Re/Os ratios in mantle peridotite and late-stage core formation</title><author><name sortKey="Gaetani, Glenn A" sort="Gaetani, Glenn A" uniqKey="Gaetani G" first="Glenn A" last="Gaetani">Glenn A. Gaetani</name><affiliation><mods:affiliation>Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA</mods:affiliation></affiliation></author><author><name sortKey="Grove, Timothy L" sort="Grove, Timothy L" uniqKey="Grove T" first="Timothy L" last="Grove">Timothy L. Grove</name><affiliation><mods:affiliation>Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA</mods:affiliation></affiliation></author></analytic><monogr></monogr><series><title level="j">Earth and Planetary Science Letters</title><title level="j" type="abbrev">EPSL</title><idno type="ISSN">0012-821X</idno><imprint><publisher>ELSEVIER</publisher><date type="published" when="1999">1999</date><biblScope unit="volume">169</biblScope><biblScope unit="issue">1–2</biblScope><biblScope unit="page" from="147">147</biblScope><biblScope unit="page" to="163">163</biblScope></imprint><idno type="ISSN">0012-821X</idno></series><idno type="istex">AFD1BFCF3E007EA4D7BC18803EB8BA4D13C0359F</idno><idno type="DOI">10.1016/S0012-821X(99)00062-X</idno><idno type="PII">S0012-821X(99)00062-X</idno></biblStruct></sourceDesc><seriesStmt><idno type="ISSN">0012-821X</idno></seriesStmt></fileDesc><profileDesc><textClass></textClass><langUsage><language ident="en">en</language></langUsage></profileDesc></teiHeader><front><div type="abstract" xml:lang="en">This study investigates the effects of variations in the relative fugacities of oxygen and sulfur on the wetting of mantle olivine by molten sulfide. Experiments were performed on mixtures of San Carlos olivine and synthetic FeS at 1 bar and 1350°C. Crucibles were fabricated from San Carlos olivine, and the fugacities of oxygen and sulfur were controlled by mixing CO2, CO, and SO2 gases. Experimental conditions ranged from logfO2=−7.9 to −10.3 and from logfS2=−1.5 to −2.5. Our experimental results demonstrate that, at a given temperature and pressure, the olivine–sulfide melt dihedral angle is controlled by the concentration of O dissolved in an anion-rich melt. Trace amounts of O dissolve in sulfide melt at fO2 conditions near the iron–wüstite oxygen buffer and the dihedral angle is 90°. At fO2 conditions near the fayalite–magnetite–quartz oxygen buffer the concentration of dissolved O is near 9 wt% and the dihedral angle is 52°, allowing small amounts of sulfide melt to form an interconnected network in olivine-rich rocks and to migrate via porous flow. These results indicate that sulfide melt is likely to be mobile at current upper mantle fO2 and fS2 conditions. In mantle peridotite, the addition or removal of sulfide melt by porous flow will variably fractionate Re/Os, U/Pb, and Th/Pb ratios because Os and Pb are more chalcophile than Re, U, and Th. The Re/Os ratio of the peridotite is especially sensitive to this process. The mobility of sulfide melt at oxidizing conditions implies that the addition of oxidized chondritic material during the later stages of the accretion of the Earth may have facilitated the segregation of core-forming material by porous flow if temperatures were in excess of the sulfide solidus.</div></front></TEI><istex><corpusName>elsevier</corpusName><author><json:item><name>Glenn A Gaetani</name><affiliations><json:string>Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA</json:string></affiliations></json:item><json:item><name>Timothy L Grove</name><affiliations><json:string>Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA</json:string></affiliations></json:item></author><subject><json:item><lang><json:string>eng</json:string></lang><value>olivine</value></json:item><json:item><lang><json:string>eng</json:string></lang><value>sulfides</value></json:item><json:item><lang><json:string>eng</json:string></lang><value>melts</value></json:item><json:item><lang><json:string>eng</json:string></lang><value>Re/Os</value></json:item><json:item><lang><json:string>eng</json:string></lang><value>core</value></json:item></subject><language><json:string>eng</json:string></language><originalGenre><json:string>Full-length article</json:string></originalGenre><abstract>This study investigates the effects of variations in the relative fugacities of oxygen and sulfur on the wetting of mantle olivine by molten sulfide. Experiments were performed on mixtures of San Carlos olivine and synthetic FeS at 1 bar and 1350°C. Crucibles were fabricated from San Carlos olivine, and the fugacities of oxygen and sulfur were controlled by mixing CO2, CO, and SO2 gases. Experimental conditions ranged from logfO2=−7.9 to −10.3 and from logfS2=−1.5 to −2.5. Our experimental results demonstrate that, at a given temperature and pressure, the olivine–sulfide melt dihedral angle is controlled by the concentration of O dissolved in an anion-rich melt. Trace amounts of O dissolve in sulfide melt at fO2 conditions near the iron–wüstite oxygen buffer and the dihedral angle is 90°. At fO2 conditions near the fayalite–magnetite–quartz oxygen buffer the concentration of dissolved O is near 9 wt% and the dihedral angle is 52°, allowing small amounts of sulfide melt to form an interconnected network in olivine-rich rocks and to migrate via porous flow. These results indicate that sulfide melt is likely to be mobile at current upper mantle fO2 and fS2 conditions. In mantle peridotite, the addition or removal of sulfide melt by porous flow will variably fractionate Re/Os, U/Pb, and Th/Pb ratios because Os and Pb are more chalcophile than Re, U, and Th. The Re/Os ratio of the peridotite is especially sensitive to this process. The mobility of sulfide melt at oxidizing conditions implies that the addition of oxidized chondritic material during the later stages of the accretion of the Earth may have facilitated the segregation of core-forming material by porous flow if temperatures were in excess of the sulfide solidus.</abstract><qualityIndicators><score>8</score><pdfVersion>1.2</pdfVersion><pdfPageSize>546 x 746 pts</pdfPageSize><refBibsNative>true</refBibsNative><keywordCount>5</keywordCount><abstractCharCount>1747</abstractCharCount><pdfWordCount>7699</pdfWordCount><pdfCharCount>46367</pdfCharCount><pdfPageCount>17</pdfPageCount><abstractWordCount>279</abstractWordCount></qualityIndicators><title>Wetting of mantle olivine by sulfide melt: implications for Re/Os ratios in mantle peridotite and late-stage core formation</title><pii><json:string>S0012-821X(99)00062-X</json:string></pii><genre><json:string>research-article</json:string></genre><host><volume>169</volume><pii><json:string>S0012-821X(00)X0074-X</json:string></pii><pages><last>163</last><first>147</first></pages><issn><json:string>0012-821X</json:string></issn><issue>1–2</issue><genre><json:string>journal</json:string></genre><language><json:string>unknown</json:string></language><title>Earth and Planetary Science Letters</title><publicationDate>1999</publicationDate></host><categories><wos><json:string>GEOCHEMISTRY & GEOPHYSICS</json:string></wos></categories><publicationDate>1999</publicationDate><copyrightDate>1999</copyrightDate><doi><json:string>10.1016/S0012-821X(99)00062-X</json:string></doi><id>AFD1BFCF3E007EA4D7BC18803EB8BA4D13C0359F</id><score>0.032495257</score><fulltext><json:item><original>true</original><mimetype>application/pdf</mimetype><extension>pdf</extension><uri>https://api.istex.fr/document/AFD1BFCF3E007EA4D7BC18803EB8BA4D13C0359F/fulltext/pdf</uri></json:item><json:item><original>false</original><mimetype>application/zip</mimetype><extension>zip</extension><uri>https://api.istex.fr/document/AFD1BFCF3E007EA4D7BC18803EB8BA4D13C0359F/fulltext/zip</uri></json:item><istex:fulltextTEI uri="https://api.istex.fr/document/AFD1BFCF3E007EA4D7BC18803EB8BA4D13C0359F/fulltext/tei"><teiHeader><fileDesc><titleStmt><title level="a">Wetting of mantle olivine by sulfide melt: implications for Re/Os ratios in mantle peridotite and late-stage core formation</title></titleStmt><publicationStmt><authority>ISTEX</authority><publisher>ELSEVIER</publisher><availability><p>©1999 Elsevier Science B.V.</p></availability><date>1999</date></publicationStmt><notesStmt><note type="content">Fig. 1: Plot of logfS2 vs. logfO2 showing the conditions at which dihedral angle experiments were performed (filled circles). Diagonal solid lines are constant logf1/2s2−logf1/2O2 contours, which is a measure of the fS2/fO2 ratio derived from the equilibrium constant for reaction 5 [12]. Vertical dashed lines represent the iron–quartz–fayalite (IQF), iron–wüstite (IW), and fayalite–magnetite–quartz (FMQ) oxygen buffers at 1350°C and 1 bar. Horizontal dashed line represents the iron–iron sulfide (FeFeS) sulfur buffer 1350°C and 1 bar.</note><note type="content">Fig. 2: Comparisons of measured (filled circles) and theoretical (open circles) frequency distributions for 200 olivine–sulfide melt apparent angles from variable duration experiments carried out at logfO2=−10.3, logfS2=−1.5, and 1350°C. Theoretical distributions were calculated using the method of Harker and Parker [25], and the best match between theoretical and observed distributions was determined by minimizing χ2. Bin size is 10°.</note><note type="content">Fig. 3: Comparisons of measured (filled circles) and theoretical (open circles) frequency distributions for 200 olivine–sulfide melt apparent angles measured in experiments 72 hours in duration at logfO2 conditions from −9.5 to −7.9 and logfS2 conditions from −2.5 to −1.5 at 1350°C (Table 1). Theoretical distributions and best match between theoretical and observed distributions were calculated as in Fig. 2. Bin size is 10°.</note><note type="content">Fig. 4: Back-scattered electron image of experiment FeS-6, in which the olivine–sulfide melt dihedral angle was determined to be 52±1.4°. Dark grains are Fo89.8 olivine and the light phase is sulfide melt containing 8.6±0.6 wt% O. Scale bar is 10 μm.</note><note type="content">Fig. 5: Contours of constant fO2 (dashes) and fS2 (dots) superimposed on a portion of the system Fe–S–O at 1 bar and 1200°C illustrating the relationship between fO2 and fS2 conditions and sulfide melt composition. After Shima and Naldrett [28].</note><note type="content">Fig. 6: A portion of the (Fe + Ni + Cu)–O–S ternary comparing the compositions of sulfide melts produced experimentally in this study with those of natural sulfide globules from MORB and Loihi glasses [34].</note><note type="content">Fig. 7: (a) Plot illustrating the experimentally determined relationships among dihedral angle, the logarithm of the mole fraction of Fe1−XO component in the sulfide melt, and logf1/2S2−logf1/2O2. Solid curve shows the result from linear regression of γsolid/liquid/γsolid/solid vs. logXSulfideMeltFe1−XO that has been transformed into dihedral angles using the relationship γsolid/solid/γsolid/liquid=2cos(θ/2). Error bars are 1σ. The Fe1−XO content of the highest logf1/2S2–logf1/2O2 experiment was estimated using a linear regression of logXSulfideMeltFe1−XO vs. logf1/2S2–logf1/2O2 for the other four experiments, and error bars were calculated using the regression parameter uncertainties. Shaded region represents 1σ uncertainties on γsolid/liquid/γsolid/solid vs. logXSulfideMeltFe1−XO regression parameters transformed into dihedral angles as described above. (b) Plot illustrating the experimentally determined relationships among γsolid/liquid/γsolid/solid, the logarithm of the mole fraction of Fe1−XO component in the sulfide melt, and logf1/2S2–logf1/2O2. The γsolid/liquid/γsolid/solid ratio for each experiment was calculated from the dihedral angle determination using the relationship given above. Solid line shows the result from a linear regression of γsolid/liquid/γsolid/solid vs. logXSulfideMeltFe1−XO for the four experiments with measured O contents. Uncertainties are as in (a).</note><note type="content">Fig. 8: (a) Plot comparing the experimentally determined relationship between dihedral angle and logXSulfideMeltFe1−XO for the melts produced in this study at 1 bar (filled symbols) with that for the high-pressure melts reported by Minarik et al. [17](open symbols). Uncertainties are as in Fig. 7b. (b) Plot of anion/cation ratio vs. dihedral angle comparing sulfide liquids produced in this study with those reported by Minarik et al. [17]. Symbols and uncertainties are as in (a).</note><note type="content">Fig. 9: Plot of (a) Re/Os and (b) U/Pb and Th/Pb ratios vs. weight percent sulfide removed from mantle peridotite via porous flow. All ratios have been normalized to an arbitrary initial ratio for clarity. Dashed line represents an estimate for the wt% sulfide melt in a fertile peridotite [51]. Partition coefficients used in the calculations are listed in Table 5.</note><note type="content">Fig. 10: Plot showing primitive mantle normalized siderophile element abundances calculated for the heterogeneous accretion model of O'Neill [66]using sulfide melt–olivine partition coefficients from the experiments of Gaetani and Grove [12]carried out at 1 bar and 1350°C with logfO2=−7.9 and logfS2=−1.8 (DV=0.19; DCr=0.12; DMn=0.06; DCo=9; DNi=70; DCu=2800) or from Table 5. Primitive mantle abundances were taken from O'Neill [66]and references therein.</note><note type="content">Table 1: Experimental conditions and gas mixing proportions</note><note type="content">Table 2: Electron microprobe analyses of experimentally produced sulfide melts</note><note type="content">Table 3: Electron microprobe analyses of experimentally produced olivines</note><note type="content">Table 4: Experimentally determined dihedral angles</note><note type="content">Table 5: Sulfide melt–olivine partition coefficients used for trace element calculations</note></notesStmt><sourceDesc><biblStruct type="inbook"><analytic><title level="a">Wetting of mantle olivine by sulfide melt: implications for Re/Os ratios in mantle peridotite and late-stage core formation</title><author xml:id="author-1"><persName><forename type="first">Glenn A</forename><surname>Gaetani</surname></persName><note type="correspondence"><p>Corresponding author. Present address: Department of Earth and Environmental Sciences, Ransselaer Polytechnic Institute, Troy, NY 12180, USA. Fax: +1 518 276 8627.</p></note><affiliation>Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA</affiliation></author><author xml:id="author-2"><persName><forename type="first">Timothy L</forename><surname>Grove</surname></persName><affiliation>Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA</affiliation></author></analytic><monogr><title level="j">Earth and Planetary Science Letters</title><title level="j" type="abbrev">EPSL</title><idno type="pISSN">0012-821X</idno><idno type="PII">S0012-821X(00)X0074-X</idno><imprint><publisher>ELSEVIER</publisher><date type="published" when="1999"></date><biblScope unit="volume">169</biblScope><biblScope unit="issue">1–2</biblScope><biblScope unit="page" from="147">147</biblScope><biblScope unit="page" to="163">163</biblScope></imprint></monogr><idno type="istex">AFD1BFCF3E007EA4D7BC18803EB8BA4D13C0359F</idno><idno type="DOI">10.1016/S0012-821X(99)00062-X</idno><idno type="PII">S0012-821X(99)00062-X</idno></biblStruct></sourceDesc></fileDesc><profileDesc><creation><date>1999</date></creation><langUsage><language ident="en">en</language></langUsage><abstract xml:lang="en"><p>This study investigates the effects of variations in the relative fugacities of oxygen and sulfur on the wetting of mantle olivine by molten sulfide. Experiments were performed on mixtures of San Carlos olivine and synthetic FeS at 1 bar and 1350°C. Crucibles were fabricated from San Carlos olivine, and the fugacities of oxygen and sulfur were controlled by mixing CO2, CO, and SO2 gases. Experimental conditions ranged from logfO2=−7.9 to −10.3 and from logfS2=−1.5 to −2.5. Our experimental results demonstrate that, at a given temperature and pressure, the olivine–sulfide melt dihedral angle is controlled by the concentration of O dissolved in an anion-rich melt. Trace amounts of O dissolve in sulfide melt at fO2 conditions near the iron–wüstite oxygen buffer and the dihedral angle is 90°. At fO2 conditions near the fayalite–magnetite–quartz oxygen buffer the concentration of dissolved O is near 9 wt% and the dihedral angle is 52°, allowing small amounts of sulfide melt to form an interconnected network in olivine-rich rocks and to migrate via porous flow. These results indicate that sulfide melt is likely to be mobile at current upper mantle fO2 and fS2 conditions. In mantle peridotite, the addition or removal of sulfide melt by porous flow will variably fractionate Re/Os, U/Pb, and Th/Pb ratios because Os and Pb are more chalcophile than Re, U, and Th. The Re/Os ratio of the peridotite is especially sensitive to this process. The mobility of sulfide melt at oxidizing conditions implies that the addition of oxidized chondritic material during the later stages of the accretion of the Earth may have facilitated the segregation of core-forming material by porous flow if temperatures were in excess of the sulfide solidus.</p></abstract><textClass><keywords scheme="keyword"><list><head>Keywords</head><item><term>olivine</term></item><item><term>sulfides</term></item><item><term>melts</term></item><item><term>Re/Os</term></item><item><term>core</term></item></list></keywords></textClass></profileDesc><revisionDesc><change when="1999-02-19">Modified</change><change when="1999">Published</change></revisionDesc></teiHeader></istex:fulltextTEI><json:item><original>false</original><mimetype>text/plain</mimetype><extension>txt</extension><uri>https://api.istex.fr/document/AFD1BFCF3E007EA4D7BC18803EB8BA4D13C0359F/fulltext/txt</uri></json:item></fulltext><metadata><istex:metadataXml wicri:clean="Elsevier, elements deleted: ce:floats; body; tail"><istex:xmlDeclaration>version="1.0" encoding="utf-8"</istex:xmlDeclaration><istex:docType PUBLIC="-//ES//DTD journal article DTD version 4.5.2//EN//XML" URI="art452.dtd" name="istex:docType"><istex:entity SYSTEM="gr1" NDATA="IMAGE" name="gr1"></istex:entity><istex:entity SYSTEM="gr2" NDATA="IMAGE" name="gr2"></istex:entity><istex:entity SYSTEM="gr3" NDATA="IMAGE" name="gr3"></istex:entity><istex:entity SYSTEM="gr4" NDATA="IMAGE" name="gr4"></istex:entity><istex:entity SYSTEM="gr5" NDATA="IMAGE" name="gr5"></istex:entity><istex:entity SYSTEM="gr6" NDATA="IMAGE" name="gr6"></istex:entity><istex:entity SYSTEM="gr7" NDATA="IMAGE" name="gr7"></istex:entity><istex:entity SYSTEM="gr8" NDATA="IMAGE" name="gr8"></istex:entity><istex:entity SYSTEM="gr9" NDATA="IMAGE" name="gr9"></istex:entity><istex:entity SYSTEM="gr10" NDATA="IMAGE" name="gr10"></istex:entity></istex:docType><istex:document><converted-article version="4.5.2" docsubtype="fla"><item-info><jid>EPSL</jid><aid>5111</aid><ce:pii>S0012-821X(99)00062-X</ce:pii><ce:doi>10.1016/S0012-821X(99)00062-X</ce:doi><ce:copyright year="1999" type="full-transfer">Elsevier Science B.V.</ce:copyright></item-info><head><ce:title>Wetting of mantle olivine by sulfide melt: implications for Re/Os ratios in mantle peridotite and late-stage core formation</ce:title><ce:author-group><ce:author><ce:given-name>Glenn A</ce:given-name><ce:surname>Gaetani</ce:surname><ce:cross-ref refid="CORR1">*</ce:cross-ref></ce:author><ce:author><ce:given-name>Timothy L</ce:given-name><ce:surname>Grove</ce:surname></ce:author><ce:affiliation><ce:textfn>Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA</ce:textfn></ce:affiliation><ce:correspondence id="CORR1"><ce:label>*</ce:label><ce:text>Corresponding author. Present address: Department of Earth and Environmental Sciences, Ransselaer Polytechnic Institute, Troy, NY 12180, USA. Fax: +1 518 276 8627.</ce:text></ce:correspondence></ce:author-group><ce:date-received day="21" month="7" year="1998"></ce:date-received><ce:date-revised day="19" month="2" year="1999"></ce:date-revised><ce:date-accepted day="8" month="3" year="1999"></ce:date-accepted><ce:abstract><ce:section-title>Abstract</ce:section-title><ce:abstract-sec><ce:simple-para>This study investigates the effects of variations in the relative fugacities of oxygen and sulfur on the wetting of mantle olivine by molten sulfide. Experiments were performed on mixtures of San Carlos olivine and synthetic FeS at 1 bar and 1350°C. Crucibles were fabricated from San Carlos olivine, and the fugacities of oxygen and sulfur were controlled by mixing CO<ce:inf>2</ce:inf>, CO, and SO<ce:inf>2</ce:inf> gases. Experimental conditions ranged from log<ce:italic>f</ce:italic><ce:inf>O<ce:inf>2</ce:inf></ce:inf>=−7.9 to −10.3 and from log<ce:italic>f</ce:italic><ce:inf>S<ce:inf>2</ce:inf></ce:inf>=−1.5 to −2.5. Our experimental results demonstrate that, at a given temperature and pressure, the olivine–sulfide melt dihedral angle is controlled by the concentration of O dissolved in an anion-rich melt. Trace amounts of O dissolve in sulfide melt at <ce:italic>f</ce:italic><ce:inf>O<ce:inf>2</ce:inf></ce:inf> conditions near the iron–wüstite oxygen buffer and the dihedral angle is 90°. At <ce:italic>f</ce:italic><ce:inf>O<ce:inf>2</ce:inf></ce:inf> conditions near the fayalite–magnetite–quartz oxygen buffer the concentration of dissolved O is near 9 wt% and the dihedral angle is 52°, allowing small amounts of sulfide melt to form an interconnected network in olivine-rich rocks and to migrate via porous flow. These results indicate that sulfide melt is likely to be mobile at current upper mantle <ce:italic>f</ce:italic><ce:inf>O<ce:inf>2</ce:inf></ce:inf> and <ce:italic>f</ce:italic><ce:inf>S<ce:inf>2</ce:inf></ce:inf> conditions. In mantle peridotite, the addition or removal of sulfide melt by porous flow will variably fractionate Re/Os, U/Pb, and Th/Pb ratios because Os and Pb are more chalcophile than Re, U, and Th. The Re/Os ratio of the peridotite is especially sensitive to this process. The mobility of sulfide melt at oxidizing conditions implies that the addition of oxidized chondritic material during the later stages of the accretion of the Earth may have facilitated the segregation of core-forming material by porous flow if temperatures were in excess of the sulfide solidus.</ce:simple-para></ce:abstract-sec></ce:abstract><ce:keywords class="keyword"><ce:section-title>Keywords</ce:section-title><ce:keyword><ce:text>olivine</ce:text></ce:keyword><ce:keyword><ce:text>sulfides</ce:text></ce:keyword><ce:keyword><ce:text>melts</ce:text></ce:keyword><ce:keyword><ce:text>Re/Os</ce:text></ce:keyword><ce:keyword><ce:text>core</ce:text></ce:keyword></ce:keywords></head></converted-article></istex:document></istex:metadataXml><mods version="3.6"><titleInfo><title>Wetting of mantle olivine by sulfide melt: implications for Re/Os ratios in mantle peridotite and late-stage core formation</title></titleInfo><titleInfo type="alternative" contentType="CDATA"><title>Wetting of mantle olivine by sulfide melt: implications for Re/Os ratios in mantle peridotite and late-stage core formation</title></titleInfo><name type="personal"><namePart type="given">Glenn A</namePart><namePart type="family">Gaetani</namePart><affiliation>Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA</affiliation><description>Corresponding author. Present address: Department of Earth and Environmental Sciences, Ransselaer Polytechnic Institute, Troy, NY 12180, USA. Fax: +1 518 276 8627.</description><role><roleTerm type="text">author</roleTerm></role></name><name type="personal"><namePart type="given">Timothy L</namePart><namePart type="family">Grove</namePart><affiliation>Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA</affiliation><role><roleTerm type="text">author</roleTerm></role></name><typeOfResource>text</typeOfResource><genre type="research-article" displayLabel="Full-length article"></genre><originInfo><publisher>ELSEVIER</publisher><dateIssued encoding="w3cdtf">1999</dateIssued><dateModified encoding="w3cdtf">1999-02-19</dateModified><copyrightDate encoding="w3cdtf">1999</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 lang="en">This study investigates the effects of variations in the relative fugacities of oxygen and sulfur on the wetting of mantle olivine by molten sulfide. Experiments were performed on mixtures of San Carlos olivine and synthetic FeS at 1 bar and 1350°C. Crucibles were fabricated from San Carlos olivine, and the fugacities of oxygen and sulfur were controlled by mixing CO2, CO, and SO2 gases. Experimental conditions ranged from logfO2=−7.9 to −10.3 and from logfS2=−1.5 to −2.5. Our experimental results demonstrate that, at a given temperature and pressure, the olivine–sulfide melt dihedral angle is controlled by the concentration of O dissolved in an anion-rich melt. Trace amounts of O dissolve in sulfide melt at fO2 conditions near the iron–wüstite oxygen buffer and the dihedral angle is 90°. At fO2 conditions near the fayalite–magnetite–quartz oxygen buffer the concentration of dissolved O is near 9 wt% and the dihedral angle is 52°, allowing small amounts of sulfide melt to form an interconnected network in olivine-rich rocks and to migrate via porous flow. These results indicate that sulfide melt is likely to be mobile at current upper mantle fO2 and fS2 conditions. In mantle peridotite, the addition or removal of sulfide melt by porous flow will variably fractionate Re/Os, U/Pb, and Th/Pb ratios because Os and Pb are more chalcophile than Re, U, and Th. The Re/Os ratio of the peridotite is especially sensitive to this process. The mobility of sulfide melt at oxidizing conditions implies that the addition of oxidized chondritic material during the later stages of the accretion of the Earth may have facilitated the segregation of core-forming material by porous flow if temperatures were in excess of the sulfide solidus.</abstract><note type="content">Fig. 1: Plot of logfS2 vs. logfO2 showing the conditions at which dihedral angle experiments were performed (filled circles). Diagonal solid lines are constant logf1/2s2−logf1/2O2 contours, which is a measure of the fS2/fO2 ratio derived from the equilibrium constant for reaction 5 [12]. Vertical dashed lines represent the iron–quartz–fayalite (IQF), iron–wüstite (IW), and fayalite–magnetite–quartz (FMQ) oxygen buffers at 1350°C and 1 bar. Horizontal dashed line represents the iron–iron sulfide (FeFeS) sulfur buffer 1350°C and 1 bar.</note><note type="content">Fig. 2: Comparisons of measured (filled circles) and theoretical (open circles) frequency distributions for 200 olivine–sulfide melt apparent angles from variable duration experiments carried out at logfO2=−10.3, logfS2=−1.5, and 1350°C. Theoretical distributions were calculated using the method of Harker and Parker [25], and the best match between theoretical and observed distributions was determined by minimizing χ2. Bin size is 10°.</note><note type="content">Fig. 3: Comparisons of measured (filled circles) and theoretical (open circles) frequency distributions for 200 olivine–sulfide melt apparent angles measured in experiments 72 hours in duration at logfO2 conditions from −9.5 to −7.9 and logfS2 conditions from −2.5 to −1.5 at 1350°C (Table 1). Theoretical distributions and best match between theoretical and observed distributions were calculated as in Fig. 2. Bin size is 10°.</note><note type="content">Fig. 4: Back-scattered electron image of experiment FeS-6, in which the olivine–sulfide melt dihedral angle was determined to be 52±1.4°. Dark grains are Fo89.8 olivine and the light phase is sulfide melt containing 8.6±0.6 wt% O. Scale bar is 10 μm.</note><note type="content">Fig. 5: Contours of constant fO2 (dashes) and fS2 (dots) superimposed on a portion of the system Fe–S–O at 1 bar and 1200°C illustrating the relationship between fO2 and fS2 conditions and sulfide melt composition. After Shima and Naldrett [28].</note><note type="content">Fig. 6: A portion of the (Fe + Ni + Cu)–O–S ternary comparing the compositions of sulfide melts produced experimentally in this study with those of natural sulfide globules from MORB and Loihi glasses [34].</note><note type="content">Fig. 7: (a) Plot illustrating the experimentally determined relationships among dihedral angle, the logarithm of the mole fraction of Fe1−XO component in the sulfide melt, and logf1/2S2−logf1/2O2. Solid curve shows the result from linear regression of γsolid/liquid/γsolid/solid vs. logXSulfideMeltFe1−XO that has been transformed into dihedral angles using the relationship γsolid/solid/γsolid/liquid=2cos(θ/2). Error bars are 1σ. The Fe1−XO content of the highest logf1/2S2–logf1/2O2 experiment was estimated using a linear regression of logXSulfideMeltFe1−XO vs. logf1/2S2–logf1/2O2 for the other four experiments, and error bars were calculated using the regression parameter uncertainties. Shaded region represents 1σ uncertainties on γsolid/liquid/γsolid/solid vs. logXSulfideMeltFe1−XO regression parameters transformed into dihedral angles as described above. (b) Plot illustrating the experimentally determined relationships among γsolid/liquid/γsolid/solid, the logarithm of the mole fraction of Fe1−XO component in the sulfide melt, and logf1/2S2–logf1/2O2. The γsolid/liquid/γsolid/solid ratio for each experiment was calculated from the dihedral angle determination using the relationship given above. Solid line shows the result from a linear regression of γsolid/liquid/γsolid/solid vs. logXSulfideMeltFe1−XO for the four experiments with measured O contents. Uncertainties are as in (a).</note><note type="content">Fig. 8: (a) Plot comparing the experimentally determined relationship between dihedral angle and logXSulfideMeltFe1−XO for the melts produced in this study at 1 bar (filled symbols) with that for the high-pressure melts reported by Minarik et al. [17](open symbols). Uncertainties are as in Fig. 7b. (b) Plot of anion/cation ratio vs. dihedral angle comparing sulfide liquids produced in this study with those reported by Minarik et al. [17]. Symbols and uncertainties are as in (a).</note><note type="content">Fig. 9: Plot of (a) Re/Os and (b) U/Pb and Th/Pb ratios vs. weight percent sulfide removed from mantle peridotite via porous flow. All ratios have been normalized to an arbitrary initial ratio for clarity. Dashed line represents an estimate for the wt% sulfide melt in a fertile peridotite [51]. Partition coefficients used in the calculations are listed in Table 5.</note><note type="content">Fig. 10: Plot showing primitive mantle normalized siderophile element abundances calculated for the heterogeneous accretion model of O'Neill [66]using sulfide melt–olivine partition coefficients from the experiments of Gaetani and Grove [12]carried out at 1 bar and 1350°C with logfO2=−7.9 and logfS2=−1.8 (DV=0.19; DCr=0.12; DMn=0.06; DCo=9; DNi=70; DCu=2800) or from Table 5. Primitive mantle abundances were taken from O'Neill [66]and references therein.</note><note type="content">Table 1: Experimental conditions and gas mixing proportions</note><note type="content">Table 2: Electron microprobe analyses of experimentally produced sulfide melts</note><note type="content">Table 3: Electron microprobe analyses of experimentally produced olivines</note><note type="content">Table 4: Experimentally determined dihedral angles</note><note type="content">Table 5: Sulfide melt–olivine partition coefficients used for trace element calculations</note><subject><genre>Keywords</genre><topic>olivine</topic><topic>sulfides</topic><topic>melts</topic><topic>Re/Os</topic><topic>core</topic></subject><relatedItem type="host"><titleInfo><title>Earth and Planetary Science Letters</title></titleInfo><titleInfo type="abbreviated"><title>EPSL</title></titleInfo><genre type="journal">journal</genre><originInfo><dateIssued encoding="w3cdtf">19990530</dateIssued></originInfo><identifier type="ISSN">0012-821X</identifier><identifier type="PII">S0012-821X(00)X0074-X</identifier><part><date>19990530</date><detail type="volume"><number>169</number><caption>vol.</caption></detail><detail type="issue"><number>1–2</number><caption>no.</caption></detail><extent unit="issue pages"><start>1</start><end>208</end></extent><extent unit="pages"><start>147</start><end>163</end></extent></part></relatedItem><identifier type="istex">AFD1BFCF3E007EA4D7BC18803EB8BA4D13C0359F</identifier><identifier type="DOI">10.1016/S0012-821X(99)00062-X</identifier><identifier type="PII">S0012-821X(99)00062-X</identifier><accessCondition type="use and reproduction" contentType="copyright">©1999 Elsevier Science B.V.</accessCondition><recordInfo><recordContentSource>ELSEVIER</recordContentSource><recordOrigin>Elsevier Science B.V., ©1999</recordOrigin></recordInfo></mods></metadata><serie></serie></istex></record>Pour manipuler ce document sous Unix (Dilib)
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