Mirandaylmfos4.0

1DissectingtheRe-OsmolybdenitegeochronometerFernandoBarra1,ArturDeditius2,MartinReich1,MattR.
Kilburn3,PaulGuagliardo3&MalcolmP.
Roberts3Rheniumandosmiumisotopeshavebeenusedfordecadestodatetheformationofmolybdenite(MoS2),acommonmineralinoredepositsandtheworld'smainsourceofmolybdenumandrhenium.
Understandingthedistributionofparent187Reandradiogenicdaughter187Osisotopesinmolybdeniteiscriticalininterpretingisotopicmeasurementsbecauseitcancompromisetheaccuratedeterminationandinterpretationofmineralizationages.
Inordertoresolvethecontrolsonthedistributionoftheseelements,chemicalandisotopemappingofMoS2grainsfromrepresentativeporphyrycopper-molybdenumdepositswereperformedusingelectronmicroprobeandnano-scalesecondaryionmassspectrometry.
Ourresultsshowaheterogeneousdistributionof185,187Reand192OsisotopesinMoS2,andthatboth187Reand187Osisotopesarenotdecoupledaspreviouslythought.
WeconcludethatReandOsarestructurallyboundorpresentasnanoparticlesinornexttomolybdenitegrains,recordingacomplexformationhistoryandhinderingtheuseofmicrobeamtechniquesforRe-Osmolybdenitedating.
Ourstudyopensnewavenuestoexploretheeffectsofisotopenuggetingingeochronometers.
Oredepositsarethemainsourceofmetalsforsociety,andtheirefficientandsustainableexplorationrequiresapreciseunderstandingofthefactorsthatcontroltheirdistributionwithintheuppercrust.
ApplicationoftheRe-Osisotopicsystemhasrevolutionizedoredepositresearchsincethe1990'sbyaddressingtwoofthemostcriticalissuesinthedevelopmentofgeneticmodelsandstrategicexplorationplans:thesourceofmetalsandtheageofmineralization1–5.
Rhenium187isradioactiveanddecaystoradiogenic187Osbybetaemission.
TheRe-Ossystemfollowsthelawofradioactivitywherethetotalnumberof187Osatomsinthesampleatthepresenttimeisequaltothenum-berofatomsof187Osincorporatedinthesampleatthetimeofmineralformationandthe187Osatomsproducedbydecayofthe187Reparentradionuclide.
Duetotheirchalcophileaffinityandbehaviorduringpartialmeltingofthemantle,ReandOswillbeconcentratedinsulphidephasesusuallyatlowppbandpptlevels,respectively.
However,molybdenite(MoS2)themostcommonmolybdenumoremineralconstitutesaparticularcasewithinsulphidemineralsbecauseitcontainshighRe(intheppmrange)and187Os(atppblevels),butalmostnoinitialorcommon187Os,henceall187Osinmolybdeniteisofradiogenicorigin(i.
e.
producedfromdecayof187Re)1,2,5.
TheseuniquecharacteristicsexplainwhyRe-Osmolybdenitedatingusingthewholemineralapproachiscurrentlythemostwidelyusedsinglemineralgeochronometerinoredeposits,wherereliablecrystallizationageshavebeenobtainedbythedirectmeasurementof187Reand187Osconcentrationsinthemineral.
Althoughthepotentialofmolybdeniteasasingle-mineralgeochronometerwasrecognizedyearsago6,7,initialstudieswerehamperedbyspuriousagesthatwereinterpretedasopensystembehavioroftheisotopicsystem8,9.
Furthermore,someresearchershavesuggestedthat187Reand187Osisotopesarenotspatiallylinkedatthemicro-scaleinmolybdeniteprecludingtheuseofmicrobeammethodsforRe-Osdating10–12.
IthasbeenarguedthatthisisotopicdecouplingofReandOsiscausedbyradiogenic187Osdiffusionwhichmayaccumulateincrystaldeformationsites11.
Hence,toobtainaccurateandreliableages,wholemolybdenitecrystalsshouldbeanalyzedinordertoovercometheinferreddecoupling11,12.
HereweinvestigatethedistributionofReandOsinmolybdenite,thedegreeofisotopicandchemicalzoningoftheseelements,theformationofRe-,Os-richdomainsandparticlesinornexttomolybdenite,andthepro-cessesresponsibleforintracrystalline/intragrainfractionation.
UnderstandingthecontrolsonReandOsisotope1DepartmentofGeologyandAndeanGeothermalCenterofExcellence(CEGA),FCFM,UniversidaddeChile,PlazaErcilla803,Santiago,Chile.
2SchoolofEngineeringandInformationTechnology,MurdochUniversity,90SouthStreet,Murdoch,WesternAustralia,6150,Australia.
3CentreforMicroscopy,CharacterisationandAnalysis,TheUniversityofWesternAustralia,35StirlingHighway,Perth,WesternAustralia,6009,Australia.
CorrespondenceandrequestsformaterialsshouldbeaddressedtoF.
B.
(email:fbarrapantoja@ing.
uchile.
cl)Received:15September2017Accepted:6November2017Published:xxxxxxxxOPEN2distributioniscriticalininterpretingtheaccuracyofisotopicmeasurements,andthusexplainspuriousRe-Osagesobtainedbymicrobeamtechniques.
Tounderstandthemineralogicalformofincorporation(i.
e.
,nanoparticlesvs.
solidsolution)andtheparame-tersthatcontrolthedistributionandabundancesofReandOsinmolybdenite,weinvestigatedasuiteofsamplesfromtwoporphyryCu-Modeposits,ElAlacrán(Mexico)2,13andMiranda(Chile)14.
High-resolutionimaging,wavelength-dispersivespectroscopy(WDS)elementalandNanoSIMSisotopicmappingprovidethefirstviewofthedistributionoftheReandOselementsandtheirrespectiveisotopesatthemicrotonanometerscale.
ThesampleswerepreviouslyanalyzedforReandOsusingN-TIMS2,14andwereselectedbecauseoftheirhighReandOscontent(SupplementaryTable1),whichfacilitatetheirdetectionbyEMPAandNanoSIMS.
ResultsElementaldistributioninmolybdenite.
Quantitative,wavelength-dispersive(WDS)X-raycomposi-tionalmapsofMo,Fe,S,Re,andOsshowhomogeneousdistributionofSandMo,whereasReandOsareheter-ogeneouslydistributedwithinmolybdenitecrystals(Fig.
1andSupplementaryFig.
1).
SampleMiranda2569displaysalternating,parallelRe-rich(7,000–9,000ppm)andRe-poor(1,800–5,000ppm)zonesperpendiculartothegrowthdirectionofthec-axis(0001)ofmolybdenite(hexagonal,spacegroupP63/mmc).
Thehighest(upto15,000ppm)relativelyhomogenousReconcentrationsoccurasanovergrowthFigure1.
WDSmapsforsulfur(right)andrhenium(left)inmolybdenitegrains.
Sulfurdistributionishomogeneousinthemolybdenitecrystal,whereasrheniumshowsdifferentpatternsofdistribution.
Warmercolorsrepresenthigherconcentrations.
3overtheprimarymolybdeniteindicatingasecondRe-richeventofcrystallization(Fig.
1B).
Thisovergrowthwasformedbyalaterhydrothermaleventandisnotevidentfromroutineopticalinspection.
Rheniuminmolyb-denitefromElAlacránhasabimodaldistribution.
InsampleAlacrán-B6,Re(700–7,200ppm)accumulatesindiscretemicro-tonano-inclusionsandorsubmicronzones(Fig.
1D),whereasinsampleAlacrán-B9rheniumpartitionsintooscillatoryzoningsimilartosampleMiranda2569,withprimarymolybdenitedepletedinRe(4,000–8,000ppm),andsecondarymolybdeniteenrichedintheelement(10,000–21,500ppm;SupplementaryData1).
Additionally,highReconcentrationsareobservedattheedgesofthecentralcrystal,indicatingover-growths(Fig.
1F).
Thepatternisundisturbedbydeformationandfragmentation.
TheamountsofOs,whichweredetectedinseveralEMPAanalysesinallsamples,varyfrom400–700ppm.
ThisparticulatedistributioncombinedwithsinglespotmaximaontheOselementalmapsuggeststhepresenceofsubmicronOs-bearinginclusions(SupplementaryFig.
1andSupplementaryData1).
Rheniumandosmiumisotopesinmolybdenite.
Highspatialresolutionisotopicmappingofselectedareas(50*50μm)included98Mo,185Re,192Os,andmass187,whichrepresentsthecombinationofthetwounre-solvableisotopes187Osand187Re(Fig.
2).
Iron-(56),63Cu,107Agisotopeswerealsomonitoredinsomeareasinordertodeterminemineralogical/isotopicassociationswithReandOs.
Rhenium-185isotopemaprevealedoscil-latoryzoninginmolybdenite,whichispresentinallanalyzedsamples,includinghighly-deformedgrains(Fig.
2).
AllsamplesshowzoneswithrelativelyhighRecontent.
SampleAlacrán-B9hostsRe-richnano-inclusions(1*1017ions/cm2.
Duetothegeometryofthemassspectrometer,itwasnotpossibletocollectalltherelevantisotopessimultane-ously,thuseachareawasmappedtwiceusingtwodifferentconfigurationsofthemulticollectionsystem.
Themagneticfieldwasfixed,andtheelectronmultiplier(EM)detectorswerepositionedtocollectsignalfrom56Fe,63Cu,98Mo,107Ag,185Re,190Osduringthefirstrun,andthenthelasttwodetectorsweremovedtocollect187Reand192Osduringthesecondrun.
ThepeakpositionswerecalibratedusingpureReandOsmetalstandards.
Assensi-tivitywasakeyissueandtherewerenosignificantmassinterferences,noslitswereusedinthemassspectrometer.
Imageswereacquiredwitharastersizeof45or50μm2,ataresolutionof512*512pixels,withadwelltimesof25or30ms/pixel.
Mapswerecorrectedfor44nsdeadtimeoneachindividualpixel.
ImageswereprocessedusingtheOpenMIMSpluginforFIJI/ImageJ(https://github.
com/BWHCNI/OpenMIMS).
References1.
McCandless,T.
E.
&Ruiz,J.
Rhenium-OsmiumevidenceforregionalmineralizationinsouthwesternNorth-America.
Science261,1282–1286(1993).
2.
Barra,F.
etal.
LaramidePorphyryCu-MomineralizationinnorthernMexico:AgeconstraintsfromRe-Osgeochronologyinmolybdenite.
Econ.
Geol.
100,1605–1616(2005).
3.
Kirk,J.
,Ruiz,J.
,Chesley,J.
,Walshe,J.
&England,G.
AmajorArchean,gold-andcrust-formingeventintheKaapvaalcraton,SouthAfrica.
Science297,1856–1858(2002).
4.
Mathur,R.
,Ruiz,J.
&Munizaga,F.
RelationshipbetweencoppertonnageofChileanbase-metalporphyrydepositsandOsisotoperatios.
Geology28,555–558(2000).
5.
Stein,H.
,Markey,R.
J.
,Morgan,J.
W.
,Hannah,J.
L.
&Scherstén,A.
TheremarkableRe-Oschronometerinmolybdenite:howandwhyitworks.
TerraNova13,479–486(2001).
6.
Herr,W.
,H.
Hintenberg,H.
&Voshage,H.
Half-lifeofrhenium.
Phys.
Rev.
95,1691(1954).
7.
Luck,J.
M.
&Allegre,C.
J.
Thestudyofmolybdenitesthroughthe187Re–187Oschronometer.
EarthPlanet.
Sci.
Lett.
61,291–296(1982).
8.
McCandless,T.
E.
,Ruiz,J.
&Campbell,A.
R.
Rheniumbehaviorinmolybdeniteinhypogeneandnear-surfaceenvironments:implicationsforRe-Osgeochronology.
Geochim.
Cosmochim.
Acta57,889–905(1993).
9.
Suzuki,K.
,Kagi,H.
,Nara,M.
,Takano,B.
&Nozaki,Y.
Experimentalalterationofmolybdenite:evaluationoftheRe-Ossystem,infraredspectroscopicprofileandpolytype.
GeochimCosmochimActa64,223–232(2000).
10.
Koler,J.
etal.
LaserablationICP-MSmeasurementsofRe/OsinmolybdeniteandimplicationsforRe-Osgeochronology.
Can.
Mineral.
41,307–320(2003).
11.
Stein,H.
,Scherstén,A.
,Hannah,J.
&Markey,R.
Subgrain-scaledecouplingofReand187OsandassessmentoflaserablationICP-MSspotdatinginmolybdenite.
Geochim.
Cosmochim.
Acta67,3673–3686(2003).
12.
Selby,D.
&Creaser,R.
A.
MacroscaleNTIMSandmicroscaleLA-MC-ICP-MSRe-Osisotopicanalysisofmolybdenite:TestingspatialrestrictionsforreliableRe-Osagedeterminations,andimplicationsforthedecouplingofReandOswithinmolybdenite.
Geochim.
Cosmochim.
Acta68,3897–3908(2004).
13.
Dean,D.
A.
Geology,alteration,andmineralizationoftheElAlacránarea,NorthernSonora,Mexico:UnpublishedM.
S.
Thesis,UniversityofArizona,TucsonArizona,222pp.
14.
Barra,F.
etal.
TimingandformationofporphyryCu–MomineralizationintheChuquicamatadistrict,northernChile:newconstraintsfromtheTokicluster.
Miner.
Deposita48,629–651(2013).
15.
Voudoris,P.
C.
etal.
Rhenium-richmolybdeniteandrheniiteinthePagoniRachiMo-Cu-Te-Ag-Auprospect,northernGreece:ImplicationsfortheRegeochemistryofporphyry-styleCu-MoandMomineralization.
Can.
Mineral.
47,1013–1036(2009).
16.
Ciobanu,C.
L.
etal.
Traceelementheterogeneityinmolybdenitefingerprintsstagesofmineralization.
Chem.
Geol.
347,175–189(2013).
17.
Grabezhev,A.
I.
&Voudoris,P.
G.
RheniumdistributioninmolybdenitefromtheVosnesenskporphyryCu±(Mo,Au)deposit(southernUrals,Russia).
Can.
Mineral.
52,671–686(2014).
18.
Shore,M.
&Fowler,A.
D.
Oscillatoryzoninginminerals:acommonphenomenon.
Can.
Mineral.
34,1111–1126(1996).
19.
Watson,E.
B.
Surfaceenrichmentandtrace-elementuptakeduringcrystalgrowth.
Geochim.
Cosmochim.
Acta60,5013–5020(1996).
20.
Holten,T.
,Jamtveit,B.
&Meakin,P.
Noiseandoscillatoryzoningofmineral.
Geochim.
Cosmochim.
Acta64,1893–1904(2000).
21.
O'Driscoll,B.
&González-Jiménez,J.
M.
"Petrogenesisofplatinum-groupelements"inHighlySiderophileandStronglyChalcophileElementsinHigh-TemperatureGeochemistryandCosmochemistry(eds.
Harvey,J.
&DayM.
D.
)489–578(MSA2016).
22.
González-Jiménez,J.
M.
&Reich,M.
Anoverviewoftheplatinum-groupelementnanoparticlesinmantle-hostedchromitedeposits.
OreGeol.
Rev.
81,1236–1248(2017).
23.
Reich,M.
etal.
Thermalbehaviorofmetalnanoparticlesingeologicmaterials.
Geology.
34,1033–1036(2006).
24.
Barker,S.
L.
L.
etal.
Uncloaking"invisible"gold:useofNanoSIMStomeasuregold,traceelementandsulfurisotopesinpyritefromCarlin-typegolddeposits.
Econ.
Geol.
104,897–904(2009).
25.
Reich,M.
etal.
"Invisible"silverandgoldinsupergenechalcocite.
Geochim.
Cosmochim.
Acta74,6157–6173(2010).
26.
Xiong,Y.
&Wood,S.
A.
ExperimentaldeterminationofthesolubilityofReO2andthedominantoxidationstateofrheniuminhydrothermalsolutions.
Chem.
Geol.
158,245–256(1999).
27.
Berzina,A.
N.
,Sotnikova,V.
I.
,Economou-Eliopoulos,M.
&Eliopoulos,D.
G.
DistributionofrheniuminmolybdenitefromporphyryCu–MoandMo–CudepositsofRussia(Siberia)andMongolia.
OreGeol.
Rev.
26,91–113(2005).
28.
Kusiak,M.
A.
,Whitehouse,M.
J.
,Wilde,S.
A.
,Nemchin,A.
A.
&Clark,C.
MobilizationofradiogenicPbinzirconrevealedbyionimaging:ImplicationsforearlyEarthgeochronology.
Geology41,291–294(2013).
29.
Valley,J.
W.
etal.
Hadeanageforapost-magma-oceanzirconconfirmedbyatom-probetomography.
Nat.
Geosci.
7,219–223(2014).
30.
Kusiak,M.
A.
etal.
Metallicleadnanospheresdiscoveredinancientzircons.
Proc.
Natl.
Acad.
Sci.
USA112,4958–4963(2015).
31.
Donovan,J.
J.
&Tingle,T.
N.
Animprovedmeanatomicnumbercorrectionforquantitativemicroanalysis.
JMicros2,1–7(1996).
32.
Armstrong,J.
T.
Quantitativeanalysisofsilicatesandoxideminerals:ComparisonofMonte-Carlo,ZAFandPhi-Rho-ZproceduresinMicrobeamanalysis(ed.
Newberry,D.
E.
)239–246(SanFranciscoPress,1988).
33.
Donovan,J.
J.
,Snyder,D.
A.
&Rivers,M.
L.
Animprovedinterferencecorrectionfortraceelementanalysis.
MicrobeamAnalysis2,23–28(1993).
7AcknowledgementsThisworkwasfundedbyProjectFondecyt#1140780toF.
B.
andM.
R.
TheauthorsalsoacknowledgethesupportofMilleniumNucleusNC130065andCEGAFondap-Conicyt15090013.
AuthorContributionsF.
B.
designedthestudy.
A.
D.
andM.
P.
R.
performedtheEMPAanalysis,M.
R.
K.
andP.
G.
conductedthenanoSIMSanalysis.
F.
B.
,A.
D.
,M.
R.
andM.
R.
K.
discussedtheresults.
F.
B.
,A.
D.
andM.
R.
wrotethepaper.
M.
R.
K.
andM.
P.
R.
providedcommentsonthepaperbeforesubmission.
AdditionalInformationSupplementaryinformationaccompaniesthispaperathttps://doi.
org/10.
1038/s41598-017-16380-8.
CompetingInterests:Theauthorsdeclarethattheyhavenocompetinginterests.
Publisher'snote:SpringerNatureremainsneutralwithregardtojurisdictionalclaimsinpublishedmapsandinstitutionalaffiliations.
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