【非傳統(tǒng)穩(wěn)定同位素地球化學(xué)】07.23-Mg同位素地球化學(xué)

鎂同位素地球化學(xué)Fromthebeginning:TheUniverse:14.5GaTheSolarSystemTheMilkyWayGalaxyThePresentSolarSystem:4.567GaOnestar(TheSun)+nineplanets+asteroids+…GaseousplanetsTerrestrialplanetsMoonEarlyEarthEarlyMoonAsteroidWhenwasthepicturetaken?WastheEarthdifferentiated?WastheEarthaclosedsystem?TheEarlySolarSystemThepresentEarthishighlydifferentiatedTheoriginoftheEarthandMoon

TheevolutionoftheatmosphereMajorquestions: OriginandevolutionoftheEarthThemantledifferentiationThemakingofthecontinentalcrust…Time00.51N/N0Stableisotope:C,H,O,SLong-livedradioactiveisotope:87Rb,235U,Short-livedradioactiveisotope(26Al,60Fe,182Hf,etc.)IsotopetracersTraditionalisotopes:H,C,N,O,S Non-traditional:Li,Mg,Fe,Cu,Zn,Ti,Se,Tl…Tools:Non-TraditionalStableisotopesGas-sourcevs.MC-ICPMS(80vs.20yrs)Non-Metalvs.metalLightvs.HeavyLargeconcentrationvariationsintheEarthFractionationmechanisms:covalentvs.ionicTraditionalvs.Non-traditionalisotopesTraditionalisotopes:H,C,N,O,S Non-traditional:Li,Mg,Fe,Cu,Zn,Ti,Se,Tl…Tools:Non-TraditionalStableisotopesTheoriginoftheEarthandMoon

TheevolutionoftheatmosphereThemantledifferentiationThemakingofthecontinentalcrust…Giant-impactTheory Riseofatmosphericoxygen MagmatransportrateContinentalweatheringNon-traditionalisotopescanhelpanswerallofthesemajorquestions有什么問題沒有？MagnesiumisotopegeochemistryR(Li+)R(Mg2+)Coordinatetype4-fold0.73?8-fold6-fold0.71?0.90?0.86?1.03?1.06?R(Fe2+)0.77?0.92?1.06?MagnesiumcrystalchemistrySimilartoferrousFeandLiLisubstitutesMgandFeFeandMginterchangeablei.e.,solidsolutionMagnesiumelementaldistribution“Geochemistry”byBillWhiteContinentalcrustMgO=5wt.%Bt,Hbl,PxOceaniccrustMgO=8wt.%Px,OlMantleMgO=38wt.%Ol,PxHydrosphereSeawaterRiverwaterContinentalcrust:granodiorite:biotite,hornblende,pyroxeneOceaniccrust:basalt:pyroxene,olivineMantle:peridotite:olivine,pyroxeneRock-formingmineralsMagnesiumelementaldistributionMagnesium(24Mg,25Mg,26Mg)Highabundancedistributionhigh-precisionanalysis>8%massdifferencelargemass-dependentfractionation26Al-26Mg(t1/2=0.73Myr)26Al-26Mg(t1/2=0.73Myr)2.Numberof26Alalivetoday:NT=0=(1/2)6164xNT=4.5bya=0Q:Howmuchis26AlintheEarthtoday?1.Halflife:t1/2=0.73MyrA:3.Afterfivehalflives,radioactiveisotopesaregone4.Al-MgsystemcanonlybeusedtodateeventsintheearlysolarsystemMass-dependentMgisotopefractionationDSM3,Galyetal.(2003)-1]x103d26Mg=[(26Mg/24Mg)sample(26Mg/24Mg)DSM3-1]x103d25Mg=[(25Mg/24Mg)sample(25Mg/24Mg)DSM3Mass-dependentisotopefractionation(26-24)/(25-24)=2/1Tengeta.2010GCAd25Mg=0.516xd26Mg Whatwillitlooklikeifyouhave26Mgproducedbydecayof26Al?Mass-dependentisotopefractionation(26-24)/(25-24)=2/1Tengeta.2010GCAd25Mg=0.516xd26Mg Radiogenic26Mg?MagnesiumisotopicsystematicsofchondrulesandCAIsfromAllende,Murchison,MurrayandBjurboleF.-Z.Teng,M.Wadhwa,P.E.Janney,L.Grossman,S.Simon,andN.DauphasAcknowledgments:A.M.Davis,F.M.Richter,E.MullaneLPSCMarch12,20072008年去阿肯色大學(xué)同樣樣品，但是用溶液法分析的，證明下面文章錯(cuò)誤ChondriticMgisotopiccompositionoftheEarthChondriticMgisotopiccompositionoftheEarthNon-chondriticMgisotopiccompositionoftheEarthDebatesonMgisotopiccompositionoftheEarthChondritic:(Normanetal.2006;Tengetal.2007;Handleretal. 2009;Huangetal.09;Yangetal.2009)Non-chondritic:(WiechertandHalliday2007;Youngetal.2009) “TheEarthisupto0.3‰heavierthanchondrites”II.MagnesiumisotopefractionationinmantlerocksI.TheMgisotopiccompositionoftheEarthLimited:(Tengetal.2007;Handleretal.2009;Wiechertand Halliday2007;Yangetal.2009)Significant:(Pearsonetal.2006;Youngetal.2009)Whyaretheresomanydebates?Limiteddatabase: Mantlesamples&chondritesInter-laboratoryanalyticalartifacts Terrestrialsamples&chondritesThedifferencebetweenEarthandchondritesis≤0.3‰!Chondrites有什么問題沒有？Mgisotopiccompositionsofmajorreservoirs MgisotopefractionationOutlinePotentialapplication：李曙光院士王崢嶸教授AnalyticalmethodEarthandchondritesCrustHydrosphereWeatheringMetamorphismIgneousprocessesMagnesiumisotopecompositionoftheEarthandchondritesThepresentEarthishighlydifferentiatedHowtostudycompositionoftheEarth?PeridotitesOceanicbasaltsMgisotopiccompositionofthemantleSamples:globallydistributed,chemicallydiverseperidotitexenolithsandoceanicbasalts(n=139)n=29n=47n=63Tengetal.2010GCAMagnesiumisotopiccompositionsofMORBsTengetal.2010GCAHomogenousd26MgMagnesiumisotopiccompositionsofOIBsTengetal.2010GCAHomogenousd26MgMagnesiumisotopiccompositionofperidotiteTengetal.2010GCAHomogenousd26MgMgisotopiccompositionofthemantle=d26MgMORB=d26MgOIBd26MgperidotiteTengetal.2010GCAd26Mgofchondrites:AhomogeneousreservoirPrimaryandsecondaryprocessesthataffectedchemicalandLi,OandSiisotopiccompositionsofchondritesdidnotsignificantlyfractionateMgisotopesTengetal.2010GCAComparisonofourdatavs.literaturedataforchondritesAnalyticalartifact:columnchemistry+MC-ICPMSSampleheterogeneity:differentproportionofCAIsandchondrulesTengeta.2010GCAEarthvs.Chondrites:-0.25vs.-0.28Consideringthelong-termprecision(±0.07,2SD),d26MgEarth=d26MgchondritesTengetal.2010GCAOtherstudiessuggestchondriticEarthArewedoneyet?No!2014GoldschmidtconferenceMoredebates,morechancesincludingfunding！有爭(zhēng)論，才有進(jìn)步！科學(xué)研究的使命是探索真理，就像在真理的長(zhǎng)河中游泳，而真理的長(zhǎng)河是沒有盡頭的。無論取得多大進(jìn)步，其真理性都是相對(duì)的。因此，我們要?dú)g迎批評(píng)，不可固步自封----李曙光有什么問題沒有？問題：知道地球和球粒隕石是否有相同組成有什么用呢？為什么我們爭(zhēng)來爭(zhēng)去呢？MagnesiumisotopiccompositionofcontinentalcrustUppercont.crustHowtostudycrustalcomposition?Lowercont.crustWeightedaverageofrocksexposedatthesurfaceFine-grainedclasticsedimentaryrocksorglacialdepositsLowercrustxenolithsExposedmetamorphicterranesMgisotopiccompositionoftheuppercrustMgisotopiccompositionoftheuppercrustLietal.2010GCASamples:globallydistributedloess,shaleandA-,I-andS-typegranites(n=99)China/Europe/USAPAASAustralia&ChinaWell-studiedMajorcomponentsoftheUCCMgisotopiccompositionoftheuppercrustHighlyheterogeneousHeavierthanthemantleMantleLietal.2010GCAMgisotopiccompositionofthelowercrustLowercrustalsamples:GranulitexenolithsChudleigh:ExclusivelymaficxenolithsMcBride:FelsictomaficxenolithsTengetal.2013G3Whydowestudythesexenoliths?Saaletal.,1998NatureWell-characterizedSimilarmajor/traceelementcompositionstotheLCCRudnicketal.1986;RudnickandTaylor1987;1991;RudnickandWilliams1987;RudnickandGoldstein,1990;Saaletal.1998;Tengetal.2008MgisotopiccompositionofthelowercrustTengetal.2013G3HighlyheterogeneousHeavierthanthemantleMagnesiumisotopiccompositionofhydrosphereTheonlyplanetwithwaterMgisotopiccompositionofseawaterGlobalseawaterLingetal.2011RCMMgisotopiccompositionofseawaterGlobalseawaterLingetal.2011RCMMgisotopiccompositionofsurfaceseawaterishomogenousverticallyandhorizontallyLongresidencetime,wellmixedMgisotopiccompositionofriverwaterHeterogeneousd26Mg,onaveragelighterthanseawaterKeetal.2011APSRiverwaterAve.=-1.1‰SeawaterMainlycontrolledbybedrocksSeawaterSummary:majorreservoirs有什么問題沒有？問題：知道地球各個(gè)儲(chǔ)庫(kù)組成有什么用呢？CompositionprocesshowtheplanetworksOceaniccompositionSeafloorspreadingCrustalcompositionsLCCdelaminationSeawatercompositionclimatechangeWhyisthecontinentheavierwhereasthehydrospherelighterthanthemantle?Seawater這是為什么呢？Isotopefractionation!Mgisotopiccompositionsofmajorreservoirs MgisotopefractionationOutlinePotentialapplication：李曙光院士王崢嶸教授AnalyticalmethodEarthandchondritesCrustHydrosphereWeatheringMetamorphismIgneousprocessesChemicalweathering:

DecompositionofrocksintoclaysMineralogicalchanges:1.Plagioclase,biotitewillbelostfirst2.FollowedbyK-spar,quartz3.Clayminerals(kaolinte)andFe-oxidesformChemicalchanges:Ca,Mg,NawillbelostfirstFollowedbyK,SiAlandferricFe(Fe3+)stayduringweatheringHowaboutisotopicchanges?Large!ImportanceofchemicalweatheringMaintainCO2contentofatmosphere1.CaSiO3+CO2CaCO3+SiO22.MgSiO3+CO2MgCO3+SiO2ControlchemicalcompositionofhydrosphereCa,Mg,NaandKdominatesriverwaterCa,MgNaandKdominatesseawaterAffectchemicalcompositionofthecontinentalcrustTheprotolithofcrustisbasalt,howeverThecrustisdepletedinCa,MgrelativetobasaltContinentalweatheringprofile:Saprolitesdevelopedonadiabasedike,SouthCarolina(Gardneretal1981)Tengetal.2010EPSLMgisotopefractionationduringweatheringTengetal.2010EPSLLightMgisotopespreferhydrospheretoweatheredcrust,resultinginanisotopicallylighthydrosphereandheavycrustMgisotopefractionationduringweatheringHowaboutextremeweathering?Halloysite+Fe-andAl-oxy-hydroxidesKaolinite+Fe-andAl-oxy-hydroxidesSamples:basaltweatheringprofileWellstudied(Maetal.,2007;2010)ExperiencedextremeweatheringPrimarymineralalteredintoclaymineralLocation:HainanIsland,ChinaClimate:Tropical

Basalt(60%Pl+35%Py)Huangetal.2012EPSLWeatheringincreasestowardssurfaceWeatheringintensityFreshBasalt(-0.35‰)Huangetal.2012EPSLEvenimmobileelementsaredepletedtowardssurfaceWeatheringincreasestowardssurfaceWeatheringintensityFreshBasalt(-0.35‰)Huangetal.2012EPSL>90%MgwaslostAbout1‰fractionationPositivecorrelationbetweenMgandd26MgIsotopefractionationduringsorptionLightMgisotopespreferhydrospheretoweatheredcrust,resultinginanisotopicallylighthydrosphereandheavycrustHuangetal.2012EPSLSamplesbelow3mreflectadsorptionSamplesabove3mreflectdesorptionbycationexchangeChemicalweatheringond26MgofcrustandmantleIsotopicallylightMgwaslostfromcontinentsintorivers,eventuallyoceans99.9%ofMginthemantle0.1%ofMginthecrust+hydrosphereTengetal.2010EPSL有什么問題沒有？Itisnotsurprisingtoseelargeisotopefractionationduringlow-TprocessesDohigh-TprocessesfractionateMgisotopes?NoandYesMgisotopiccompositionsofmajorreservoirs MgisotopefractionationOutlinePotentialapplication：李曙光院士王崢嶸教授AnalyticalmethodEarthandchondritesCrustHydrosphereWeatheringMetamorphismIgneousprocessesLackofMgisotopefractionationduringmetamorphicdehydrationLackofMgisotopefractionationduringmetamorphicdehydrationLietal.,2014DehydrationofmetapeliteLietal.,2014G3LackofMgisotopefractionationduringmetamorphicdehydrationLietal.,2014NofractionationduringmetamorphicdehydrationSeeTengetal.,2013G3,Wangetal.,2014GCAforregionalmetamorphismMgisotopiccompositionsofmajorreservoirs MgisotopefractionationOutlinePotentialapplication：李曙光院士王崢嶸教授AnalyticalmethodEarthandchondritesCrustHydrosphereWeatheringMetamorphismIgneousprocessesLimitedfractionationduringigneousdifferentiationLimitedfractionationduringigneousdifferentiationTengetal.2010GCA/2007EPSLHomogeneousMgisotopiccompositionofperidotite,basalt,granodioriteandgranitesuggestlimitedisotopefractionationIgneousdifferentiation(peridotite/basalt)Igneousdifferentiation(granodiorite/granite)Liuetal.2010EPSLLimitedfractionationathightemperaturesWholerocksvs.mineralsHblandBtingranitoidsLiuetal.2010EPSLLimitedinter-mineralfractionationCpx,OpxandOlinperidotiteYangetal.2009EPSLCpx,Opx,Ol,HblandBtarethemostabundantMg-richmineralsintheEarthIsotopefractionationisqualitativelycontrolledbythecoordinationnumberofMgsitesinmineralsHeavyisotopesprefermineralswithhighbondingenergysitese.g.,lowcoordinationsitesTetrahedron,CN=4,shortbondlength,highbondingenergysiteOctahedron,CN=6,longbondlength,lowbondingenergysiteEnrichedinheavyMgisotopeEnrichedinlightMgisotopeWhydothesemineralshavesimilard26Mg?But,canfindlargefractionationsathigh-TincertaincircumstancesCoordinationofMgisnot6intwoimportantrock-formingminerals:Spinel(CN=4)andGarnet(CN=8)LargeequilibriumisotopefractionationisexpectedwhenthesetwomineralsarepresentInmostrock-formingminerals(Ol,Opx,Cpx,Hbl,Bt),coordinationnumberofMgis6i.e.,inoctahedron.Hencelimitedinter-mineralfractionationisexpected.有什么問題沒有？Outline:High-TMgIsotopeFractionationEquilibriumMgisotopefractionationGarnet-omphacitethermometerSpinel-olivinethermometerDiffusion-drivenkineticMgisotopefractionationChemicaldiffusionSoretdiffusionLimitedfractionationathightemperaturesWholerocksvs.mineralsGrt-OmpequilibriumisotopefractionationWholerock:protolith-likeMgisotopiccompositionMinerals:largeMgisotopefractionationSamples:eclogitesfromDabieshanthatformedat～600oCLietal.2011EPSLTengetal.2010EPSLinreviewOmphaciteis1.14‰heavierthancoexistinggarnet!Lietal.2011EPSLGrt-OmpequilibriumisotopefractionationTengetal.2010EPSLinreviewEquilibrium,notkineticfractionationLietal.2011EPSLLackofdiffusionbetweengarnetandomphaciteDiffusivity:Mg>OOisotopeequilibriumMgisotopeequilibriumEquilibriumfractionationcontrolledbyCN:omphacitevs.garnet:6vs.8Lietal.2011EPSL,alsoseeWangetal.2013EPSL,2014GCAd26MgOmp-d26MgGrt=1000lna=A/T2Isotopefractionationbetweentwominerals(e.g.,Omp-Grt)isalinearfunctionof1/T2Grt-OmpequilibriumisotopefractionationGeothermometerTengetal.2010EPSLinreviewSamplebackground:Spl-facieslherzolitesfromNorthChinacratonformedfrom800to1150oC(two-PxCathermometry)Samplesanalyzed:whole-rockpowder(n=11)Ol,Opx,CpxandSplfragments(n=47)Spl-OlequilibriumisotopefractionationLiuetal.EPSL,2011Tengetal.2010EPSLinreviewLargetemperature-dependentisotopefractionationbetweenspinelandolivineEquilibriumfractionationcontrolledbyCNofMg:spinelvs.olivine:4vs.6Liuetal.EPSL,2011Spl-OlequilibriumisotopefractionationTengetal.2010EPSLinreviewAgreewellwiththeoreticalstudieswheneffectsofchemicalcompositionandbondingenvironmentareconsidered.Liuetal.EPSL,2011;alsoseeXiaoetal.GCA2013Spl-OlequilibriumisotopefractionationGeothermometer有什么問題沒有？Outline:High-TMgIsotopeFractionationEquilibriumMgisotopefractionationGarnet-omphacitethermometerSpinel-olivinethermometerDiffusion-drivenkineticMgisotopefractionationChemicaldiffusionSoretdiffusionLighterisotopesdiffusefasterthanheavyonesHowdoesdiffusionfractionateisotopes?D2/D1=(m1/m2)=0.5foridealgas<0.5forliquid&solidRichteretal.1999GCALighterisotopesdiffusefasterthanheavyonesAtthesameT,samekineticenergyKEave=?mivi2Thevelocityratiofortwoisotopes:v2/v1=(m1/m2)0.516O2diffuses√36/32=1.06timesfasterthan18O216O218O2Time=0Time=tLet16O2and18O2diffusethroughatube;theirdifferentdiffusivitywillseparatethem,i.e.,isotopefractionation.Howdoesdiffusionfractionateisotopes?Li/Mg/Fe/Cadiffusionbetweenbasalt(B)andrhyolite(R)meltExperimentsondiffusion-drivenfractionation

(Li,Mg,Ca,Feetc.)Richteretal.2008GCARhyoliteBasaltRichteretal.2003GCAInitialprofileInitialprofileMagnesium,iron,calciumetc.Basaltsonathermalgradient(WalkerandDelong,1982CMP)SamplesreachedasteadystateinafewdaysHeavierelements?coolerend/thelighter?hotendThechemicalconcentrationissimilartothatexpectedfromfractionalcrystallizationWalkerandDeLong,1982CMPII:ThermaldiffusionorSoreteffectII:Thermaldiffusion:ExperimentsRichteretal.2007GCARichteretal.2008GCARichteretal.2008GCARichteretal.2007II:Thermaldiffusion:MgisotopesRichteretal.2007GCAStartpositionRichteretal.2008GCAIIThermaldiffusion:IsotopesDataarefromRichteretal.2008;2009有什么問題沒有？Diffusion–drivenkineticisotopefractionationisintransientandshoulddisappearatgivenenoughtime.Isitpossibletofindsuchexamplesinnature?Diffusion-drivenMgandFeisotopefractionationinHawaiianolivineFang-ZhenTengNicolasDauphasRozHelzShanGaoShichunHuangTengetal.2008,ScienceTengetal..2011,EPSLSio,etal.,2013GCAMechanismsforproducingzonedminerals1.CrystalgrowthTengetal.2011,EPSLMechanismsforproducingzonedminerals2.DiffusionTengetal.2011,EPSLHowtotellthedifferentmechanism?CrystalgrowthDiffusionDifferentmechanismyieldstotallydifferentinformationMechanismsforproducingzonedmineralsIsotopes!1.CrystalgrowthMechanismsforproducingzonedmineralsMineralzoningreflectschangingchemicalcompositionduringmagmaticdifferentiationIsotopefractionationduringmagmaticdifferentiationislimitedElementalzoningisnotassociatedwithisotopefractionationTengetal.2011,EPSL2.DiffusionMechanismsforproducingzonedmineralsInter-diffusionexchangeofFeandMgLighterisotopesdiffusefasterthanheavyones:lighterFeinandlighterMgoutofolivineNegativecorrelationbetweend26Mgandd56FeCoupledelemental&isotopiczoningTengetal.2011,EPSLHowtotellthedifferentmechanism?CrystalgrowthDiffusionDifferentmechanismyieldstotallydifferentinformationMechanismsforproducingzonedmineralsLimitedisotopefractionationLarge,negativelycoupledisotopefractionationCoupledelemental&isotopiczoningTengetal.2011,EPSLKilaueaIkilavalake,Hawaii: AtextbookexampleofmagmadifferentiationKilaueaIkilavalakeCrystallizationPartialmeltingAssimilationFluidexsolutionSourceheterogeneityKilaueaIkilavalake,Hawaii,USABeforeeruptionAftereruptionTengetal.08ScienceHelz(1987)CrystallizationsequenceofKilaueaIkilavasMgO=11%:

primitivemagma7.5%<MgO<11%:olivine5%<MgO<7.5%:augite+plagMgO<5%:oxides11%<MgO:Olivine+primitivemagmaTengetal.08ScienceFeisotopefractionationduringbasaltdifferentiationAndesiticmeltsOlivinecumulatePrimitivemagmaMixingCrystallizationTengetal.08ScienceOlivinesareindeedlighterthanmelts!Tengetal.08ScienceWhatcausedFeisotopefractionationI.EquilibriumisotopefractionationII.Kineticisotop