ABSTRACT Titleof Document: TheMultipleSulfurIsotopicCompositionof IronMeteorites:ImplicationsforNebular Evolution. MichaelArielAntonelli,MasterofScience, 2013. DirectedBy: ProfessorJamesFarquhar,Departmentof GeologyandEarthSystemSciences InterdisciplinaryCenter,UniversityofMaryland- CollegePark Multiplesulfurisotopicmeasurementsoftroilitefrom61differentironmeteorites wereundertakeninordertotestforsulfurisotopichomogeneitywithin(andbetween) 8differentironmeteoritegroups.Itwasfoundthatdifferentmemberswithinagiven groupofironmeteoriteshavehomogeneous Δ33 Scompositions,butthatthese Δ33 S compositionsdifferbetweengroups.Thisthesisshowsthatironmeteoritesfromthe groupsIC,IIAB,IIIAB,IIIF,andIVAhavesmallyetresolvableenrichmentsor depletionsin Δ33 SrelativetoCanyonDiabloTroilite(CDT)andtroilitefromother non-magmatic(IABandIIE)ironmeteorites.Theobservedanomaloussulfurisotopic compositionsinmagmaticironmeteoritesaremostconsistentwithLyman-α photolysisofH 2S,pointingtowardsinheritanceofanunexpectedphotolytically- derivedsulfurcomponentinmagmaticironmeteoritegroupswhichisabsentinnon- magmaticironmeteorites,chondrites,andtheEarth-MoonSystem. THEMULTIPLESULFURISOTOPICCOMPOSITIONOFIRONMETEORITES: IMPLICATIONSFORNEBULAREVOLUTION By MichaelArielAntonelli ThesissubmittedtotheFacultyoftheGraduateSchoolofthe UniversityofMaryland,CollegePark,inpartialfulfillment oftherequirementsforthedegreeof MasterofScience 2013 AdvisoryCommittee: Prof.JamesFarquhar,Chair Dr.TimothyJ.McCoy Prof.RichardJ.Walker ©Copyrightby MichaelArielAntonelli 2013 Acknowledgements FirstandforemostIwouldliketothankProfessorJamesFarquharforhis endlessadviceandpositiveoutlook,whichhaveextendedfarpasttheresearch containedinthisthesis.Hisapproachtoscienceandgeneraldispositionaretruly inspirational.IwouldalsoliketothankProfessorRichardJ.Walker(UMD)andDr. TimothyJ.McCoy(SmithsonianInstitution)forsharingtheirexpertiseiniron meteoritesandhelpinggreatlyinmycosmochemicaledification. ProfessorJohnT.Wasson(UCLA)isalsoowedthanksforsharinghisideas andextensiveINAAdataontheironmeteoritesanalyzedinthisstudy,whileProf. MarkH.Thiemens(UCSD)providedvaluablehumorandanswerstomany photochemicalquestions.Dr.JabraneLabidi(IPGP)andProfessorPierreCartigny (IPGP)madeveryhelpfulcommentsonseveralfacetsofthisresearch,whileDr. MathieuTouboul(UMD)providedgreatinsightsintotheanalysisofavailableHf-W data.IwouldalsoliketothankfellowmembersoftheInstituteforSulfurIsotope Studies(ISIS)attheUniversityofMaryland(DanielL.Eldridge,BrianS.Harms,and Dr.JoostHoek)fortheirhelpinthelabandforlatenightdiscussionsregardingthe subtletiesofisotopicfractionation.Finally,Iwouldliketothankmyparentsand familyfortheirendlesssupportduringmystudies. ThisresearchwaspartlyfundedbytheNaturalSciencesandEngineeringResearch CouncilofCanada(NSERC)throughaPostGraduateScholarshiptoM.A.Antonelli (PGS-M-420592-2012),andthroughaNASACosmochemistrygranttoJ.Farquhar. ii TableofContents Acknowledgements.......................................................................................................ii TableofContents.........................................................................................................iii ListofTables.................................................................................................................v ListofFigures..............................................................................................................vi Chapter1:Introduction.................................................................................................1 1.1MeteoritesandCosmochemistry.........................................................................1 1.2Overview.............................................................................................................2 Chapter2:Background..................................................................................................4 2.1IronMeteorites....................................................................................................4 2.1.1MagmaticIronMeteoriteGroups.................................................................6 2.1.1.1TheIIABIrons......................................................................................6 2.1.1.2TheIIIABIrons.....................................................................................7 2.1.1.3TheIVAIrons.......................................................................................8 2.1.1.4TheIVBIrons........................................................................................9 2.1.1.5TheICandIIIFIrons............................................................................9 2.1.2Non-MagmaticIronMeteoriteGroups......................................................10 2.1.2.1TheIABIrons......................................................................................10 2.1.2.2TheIIEIrons.......................................................................................11 2.2SulfurIsotopeSystematics................................................................................15 2.2.1Mass-DependentFractionation..................................................................15 2.2.1.1EquilibriumIsotopeFractionation......................................................15 2.2.1.2KineticIsotopeFractionation..............................................................22 2.2.2Mass-IndependentFractionation................................................................25 2.2.2.1Shielding..............................................................................................29 2.2.2.2Caveats................................................................................................31 2.2.2.3NuclearEffects....................................................................................31 2.3SulfurIsotopesinMeteorites............................................................................31 2.3.1 δ34 SinMeteoriticMaterials.......................................................................31 2.3.2MultipleSulfurIsotopeMeasurementsinMeteorites................................33 Chapter3:Methods.....................................................................................................36 3.1SampleAcquisition...........................................................................................36 3.2SulfurExtractionandAnalysis.........................................................................38 3.2.1SulfurExtraction........................................................................................38 3.2.2FluorinationandPurificationofSF 6..........................................................39 3.2.3MassSpectrometry.....................................................................................39 3.2.4SourcesofUncertainty...............................................................................41 iii 3.2.5EvaluationofUncertainty..........................................................................44 Chapter4:Results.......................................................................................................46 4.1SulfurIsotopeRelationshipsinTroilite............................................................46 4.2Chromium-ReducibleSulfur.............................................................................50 4.3MeasurementReproducibility...........................................................................51 Chapter5:Discussion.................................................................................................54 5.1EvaluationoftheSulfurIsotopicSignals..........................................................54 5.1.1MixingandtheDefinitionof ∆33 S.............................................................54 5.1.2Post-DisruptionSpallationReactions.........................................................56 5.1.3NucleosyntheticSulfurAnomalies.............................................................57 5.1.4PhotolysisintheEarlySolarNebula.........................................................61 5.2GeochemicalConsiderations.............................................................................62 5.2.1Hf-WModelAges......................................................................................62 5.2.2VolatileElementContent...........................................................................66 5.3ModelsofSulfurIsotopicDistributionintheEarlySolarNebula....................69 5.3.1VariablePreservationofaHomogeneouslyDistributed Δ33 SCarrier.......71 5.3.2PhotolyticDepletionofanInnerSolarSystemReservoir.........................72 Chapter6:Conclusions..............................................................................................76 6.1FutureWork......................................................................................................79 AppendixA.................................................................................................................84 AppendixB.................................................................................................................86 AppendixC.................................................................................................................87 AppendixD.................................................................................................................88 AppendixE..................................................................................................................89 AppendixF..................................................................................................................90