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Abstract Volume8th Swiss Geoscience MeetingFribourg, 19th – 20th November 2010

Department ofGeosciences

2. Mineralogy-Petrology-Geochemistry

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Platform Geosciences, Swiss Academy of Science, SCNATSwiss Geoscience Meeting 2010

2. Mineralogy-Petrology-Geochemistry

Eric Reusser

Swiss Society of Mineralogy and Petrology (SSMP)

2.0 AbidiR.,Slim-ShimiN.,HatiraN.,MarignacCh.,GasquetD.,MejriZ.:Approchemicrothermométriquepourladéterminationdel’originehydrothermaldef luideminéralisateurdugisementàPb-(Zn)-Sr-Bad’ElAguiba(Tunisieseptentrional)

2.1 BaderT.,FranzL.,deCapitaniC.,RatschbacherL.,HackerB.R.,WeiseC.,PoppM.:TectonometamorphicevolutionoftheWudangComplex(centralChina)

2.2 BauerK.,VennemannT.,MulchA.:ReconstructionofNeogenepaleoelevationandpaleoclimaticconditionsoftheEuropeanAlpsandthecircum-Alpineregionbystableisotopeanalyses

2.3 Cavargna-Sani M., Epard J-L., Bussy F., Ulianov A.: Zircon U/Pb dating of the Late Carboniferous ZervreilaOrthogneiss,AdulaNappe.

2.4 Diamond L.W., Tarantola A., Stünitz H.: Effects of deviatoric stress on natural f luid inclusions in quartz: anexperimentalstudy

2.5 ElKorhA.,SchmidtS.Th.,BallèvreM.,BruguierO.:U–PbgeochronologyofanorthogneissdiscoveredwithintheHP–LTmetamorphicrocksoftheIledeGroix,ArmoricanMassif,France

2.6 HermannJ.,RubattoD.:Pre-AlpinemetamorphismintheclassicalAlpinestaurolite-garnetschistofCampolungo

2.7 Huber C., BachmannO., Dufek J.: Thermo-mechanical reactivation of locked crystalmushes:melting-inducedinternalfracturationandassimilationprocessesinmagmas

2.8 HunzikerD.,CaddickM.,ReusserE.,BurgJ-P.,MüllerE.: Theinfluenceofferric/ferrousironratiosinbulkandmineralsofblueschistsfromtheInnerMakran(SEIran)onthermobarometricrecalculations

2.9 HürlimannN.,MüntenerO.,UlmerP.:Subvolcanicmafictointermediatedike-systems:contraintsonpost-plutonicactivity(S-Adamello,N-Italy)

2.10 Katona I., SerneelsV.: Thepigmentsof themedievalpainters inFribourg: Investigationofa topqualitymuralpaintingfromtheCordeliersChurchinFribourg.

2.11 KayaniS:Combustionanalysisofameteoritedebris

2.12 KhozyemH.M.,AdatteT.,TantawyA.A.,Spangenberg J.E.,KellerG.,FöllmiK.: NatureandTempoof thePETM(Paleocene-Eocenethermalmaximum)events,newinsightsfromtheGSSPDababyiasection(Luxor,Egypt).

2.13 KocsisL.,OunisA.,ChaabaniF.,NailiS.M.:NewisotopedatafromtheLateCretaceousandPaleogenephosphatebedsoftheGafsaBasin,Tunisia

2.14 KönigD.,SerneelsV.:GeochemicalandmineralogicalexaminationsofromancruciblesfromAutun(France)

2.15 LambrechtG.,DiamondL.W.:FluidboilingandmixingduringlateststageorogenicgoldmineralizationatBrusson,NWItalianAlps

2.16 MaggettiM.,MorinD.,SerneelsV.,NeururerC.:KilnfurnituresfromthefaiencemanufactureofGranges-le-Bourg(HauteSaône,France):contrastingrecipes

2.17 MaggettiM.,RosenJ.,SerneelsV.,NeururerC.:ThefaiencemanufactureLeBoisd’Épense(North-easternFrance,18/19thcentury)

2.18 MarolfA.R.,VennemannT.W.,BonzonJ.:Forensicgeology:characterisationoflightelementstableisotopesinsoilsamplesoftheSwissPlateau

2.19 Martin L.H.J., SchmidtM.W., Hametner K., Günther D.: Element partitioning between immiscible silicate andcarbonatitemeltsbycentrifugeexperiments

2.20 Mattsson H.B., Bosshard S.A., Hetényi G., Almqvist B.S.G., Hirt A.M., Caricchi L., Caddick M.: Internal f lowstructuresincolumnarjointedbasaltfromHrepphólar,Iceland

2.21 Mavris C., Egli M., PlötzeM., Götze J., Mirabella A., Giaccai D., HaeberliW.: Mineral weathering along a soilchronosequenceinahighAlpineproglacialarea:amultipleapproach

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2.22 MeierM.F.,GrobétyB.:FumarolicaerosolsfromElChichónvolcano,Mexico

2.23 Monsef R., Emami M. H., Rashidnejad Omran N., Monsef I.: Petrogenetic evolution of Neogene volcanism innorthernUromieh-DokhtarMagmaticBelt:Insightsontheoriginofpost-collisionmagmatism

2.24 Moulas E., Connolly J., Burg J.-P., KostopoulosD.: Refining the granulite-faciesmetamorphism in theRhodopemetamorphiccomplex-Greece

2.25 OrtelliM.,MoritzR.,VoudourisP.,CoscaM.,SpangenbergJ.:TertiaryPorphyryandEpithermalAssociationoftheSapes-KassiteresDistrict,EasternRhodopes,Greece

2.26 ParmigianiA.,HuberC.,BachmannO.,ChopardB.:Reactivemultiphasef lowatthepore-scale:themeltingofacrystallineframeworkduringtheinjectionofbuoyanthotvolatiles.

2.27 PretetC.,FelisT.,SamankassouE.:Constrainingcalciumisotopefractionationincorals

2.28 RegisD.,EngiM.,RubattoD.,DarlingJ.: ComplexdynamicsintheSesiaZonesubductionsystemdeducedfrommultiplegenerationsofwhitemicaandallanite:thepowerofmicrotexturalanalysiscombinedwithpetrochronology

2.29 SerneelsV.:ThousandYearsofmassiveIronProductionintheDogonCountry(Mali,WestAfrica):Technology–Economy-Environment

2.30 SkopelitisA., SchalteggerU.,UlianovA.,BrackP.: TheAdamellobatholith (Italy): a fossilmagmachamberoraccumulationofmagmapulses?

2.31 SoulignacR.:MineralogicaltechniquesandethnoarchaeologyappliedtothestudyofsmithingslagsinMali(Africa)

2.32 TămasC.G.,MunteanuG.,CauuetB.,MutG.:MiningarchaeologicalstudiesinEasternPyrenees,France:Baillestavyironminingarea

2.33 Thierrin-MichaelG.:FossiliferouspotteryinAjoie(NWSwitzerland)andadjacentregionsfromLaTèneandGallo-romansites:Informationonproductionanddistributionthroughmicroscopicandchemicalanalyses

2.34 TrittschackR.,GrobétyB.:Insightsintothedehydroxylationkineticsoflizarditeandchrysotile

2.35 VerberneR.,UlmerP.,MüntenerO.:Calculatingrheologicpropertiesofmagmasfromfieldobservationscombinedwithexperimentaldata.

2.36 VilsF.,ElliottT., Smith-DuqueC.E.,AltJ.C.,TeagleD.:Howlongdoesseawaterandoceaniccrustinteract?

2.37 von Allmen K., Böttcher M.E., Samankassou E., Nägler T.F.: Barium isotope fractionation in natural bariummineralsandprecipitationexperiments:Afirstglimpseattheglobalbariumcycle

2.38 WestermannS.,SteinM.,MateraV.,FietN.,AdatteT.,FöllmiK.B.:PalaeoredoxchangeduringOAE1a:newinsightsfromphosphorusandredox-sensitivetraceelements

2.39 WongfunN.,FurrerG.,BrandlH.,PlötzeM.:InfluenceofextrinsicweatheringfactorsonmineraldissolutioninDammaglacierforefield

2.40 ZurfluhF.J.,HofmannB.A.,GnosE.,EggenbergerU.:Water-solublesaltsandtemperaturevariationinmeteoritesrecoveredinthehotdesertofOman

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2.0

Approchemicrothermométriquepourladéterminationdel’originehyd-rothermaldefluideminéralisateurdugisementàPb-(Zn)-Sr-Bad’ElAguiba(Tunisieseptentrional)

RiadhABIDI1,NajetSLIM-SHIMI2,NouriHATIRA3,ChrisitianMARIGNAC4,DominiqueGASQUET5,ZouhairMEJRI1

1 Faculté des sciences de Bizerte, département de géologie, Jarzouna-Bizerte.7021. Tunisie. ([email protected])2 Faculté des sciences mathématiques, physiques naturelles de Tunis. Campus Universitaire. 1060 Tunis. Tunisie.3 Faculté des sciences de Gabes (Faculté des Sciences de Gabès, Cité Riadh, Zirig 6072 Gabès)4 Ecole Nationale Supérieure des Mines de Nancy, Parc de Saurupt, 54042 Nancy, France.5 Université de Savoie – CISM Laboratoire EDYTEM Bâtiment Belledonne Campus de Technolac 73370 LE BOURGET DU LACLegîted’ElAguibareprésentel’undesplusimportantsgîtesdelazonedesf lyschs.IlestsituésurlabordureorientaledumassiftriasiqueduJebelHamra.CeTriasfaitpartiedeslamestriasiquesextrusiveslelongdel’accidentGhardimaou–CapSerrat(DécrochementsenestreorientéNE-SW),etformeavecdesterrainsargilocarbonatésd’âgecrétacés-paléocène(UnitéEdiss),unefenêtretectoniquedansl’unitéNumidienne(argilo-gréseused’âgeoligocènesupérieur-miocèneinférieur).

Lecorpsminéralisé,constituéd’unebrècheargilo-dolomitique,estsituédanslazonedebroyageentreleTriasquirepré-senteletoitdugîteetlepaléocènequireprésentelemurdugîte.Laminéralisationestdiscordanteparapportàlarocheencaissanteetseprésentesousplusieursformes:cimentdesbrèchesdedissolution,remplissagedesfracturesetdesca-vitésdedissolutiondanslesbancsdedolomienoired’âgetriasiqueetremplacementdelarocheencaissante(dolomied’âgetriasique).Cegisementprésenteuneparagenèsesimplecomposéeparlagalène,lasphalérite,lamarcasiteetlapyritequisontaccessoirementprésentsavecuneganguereprésentéeparlacélestite(gangueprincipale),labarytine,lacalciteetlequartz.

Lesmesuresmicrothermométriques,réaliséesessentiellementdansdesinclusionsprimairesetsecondairesbiphasées(li-quide+vapeur)danslacélestiteetlacalcitedugîted’ElAguiba,ontétéeffectuéessuruneplatinechauffanteréfrigéran-tedetype«LinkamMDS-600®»

1.CélestiteLasalinitéduf luidecontenudanslesinclusionsf luidesprimairesbiphasées,estcompriseentre5.41-10.36%poidséq.NaClavecunemoyennede8.13%poidséq.NaCl.Pourlesinclusionsf luidessecondairesbiphaséeslasalinitévarieentre5.56et15.96%poidséq.NaClavecunmaximumdefréquencevers8à9%poidséq.NaCl.Lacompositionduf luideenCaCl2contenudanslesinclusionsprimairesetsecondairesbiphaséesvarieentre0et3.4Wt%.CaCl2;tandisquelacompositionduf luideenNaClcontenudans les inclusionsprimairesetsecondairesvarieentre5et12Wt.%NaCl.Latempératured’homogénéisationduf luidecontenudanslesinclusionsprimairesbiphaséesvarieentre149et230°Cavecunemoyennede184°C.Pourlesinclusionssecondairesbiphasées,latempératured’homogénéisationvarieentre130et230°Cavecunetempératuremoyennede174°C.Lef luideaunedensitémoyennede1.03etunepressionmoyennede190.71bars.Lavari-ationduchangementd’étatdesphasesd’uneinclusionbiphaséedanslacélestiteestrésuméedanslafigure.1.

2.CalciteLesinclusionsf luidesprimairesbiphaséesmontrentunesalinitéquivarieentre4.03%et10.36%poidséq.NaClavecunemoyenne de 6.7 % poids éq. NaC, une composition moyenne en CaCl2 de 2.6 wt. % CaCl2 et une températured’homogénéisationquivarieentre151°et225.7°Cavecunemoyennede178°C.Danslesinclusionssecondaires,lasalinitémoyenneestde7.4%poidséq.NaCletlatempératured’homogénéisationvarieentre130.7°et240.1°Cavecunemoyennede177°C.Lef luideaunedensitémoyennede1.03etunepressionmoyennede200.34bars

Lef luideminéralisateurdugîted’ElAguibacorrespondraitdoncaunmélangeàtendanceadiabatiquedeplusieursf luideschaudsdedifférentesorigineshydrothermalesoùlatempératurerésulteseulementdumélangedef luidessanséchangedechaleuraveclarocheauxalentours.Lef luidecontenudanslacélestiteetlacalcitemontreunesalinitémoyenneàfaibleetunetempératureélevéeetvariable.Cef luideseraitunmélangedesaumuresdubassinavecunf luidemagma-tique-météorique.

Figure1.Evolutionduchangementd’étatd’unel’inclusionf luideprimairebiphasée(L+V)danslecélestitedugîted’ElAguibaaucours

ducycledecongélation.(Tctempératuredecongélation,TitempératurededébutdefusiondelaglaceetTmtemperaturedefindefu-

siondelaglace).

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2.1

TectonometamorphicevolutionoftheWudangComplex(centralChina)

BaderThomas1,FranzLeander1,deCapitaniChristian1,RatschbacherLothar2,HackerBradleyR.3,WeiseCarsten2,PoppMichael2

1 Mineralogisch-Petrographisches Institut, Universität Basel, CH-4056 Basel ([email protected])2 Institut für Geologie, Technische Universität Bergakademie Freiberg, D-09599 Freiberg3 Geological Sciences, University of California, Santa Barbara, CA-93106

Located in the Paleozoic-Mesozoic Qinling-Dabie-Sulu-belt in central China, the Wudang Complex is composed ofNeoproterozoicsiliciclasticmeta-sedimentsandmarbleswithintercalatedacidicandbasicmeta-volcanicsandisoverlainbyCambrian-Ordovicianlimestonesanddolomites.DuringtheTriassiccollisionoftheYangtzeandtheSino-Coreanplates,theWudangComplex,whichbelongstothesubductedYangtzeplate,underwentahighpressuremetamorphism.Thisstudy investigates thismetamorphic overprint combining thermodynamicmodelingusing theDOMINO-THERIAKpro-grams(deCapitani&Petrakakis2010)withconventionalgeothermobarometry.

Felsicgneisssample76017AfromthecentralpartoftheWudangComplex,displaysthepeakmetamorphicassemblagegarnet–albite–phengite–biotite–quartz–rutile.BasedongarnetcorecompositionandtheSi-contentofphengite,DOMINOmodeling (MnTNCKFMASHsystem,excessH2O)yields510°Cat1.2GPamost likelyrepresenting thepressurepeakofthePTpath.Identicalresultswereobtainedfromgarnetgneiss76032Ctaken~30kmfurthernorth.Thematrixofanothergarnetgneissfromthesameoutcropshowsaretrograderecrystallizationtostilpnomelane,albite,quartz,andminorclinozoisitepointingtoalateoverprintat~320°Cand>0.3GPa.

SeveralmetabasicschistsfromWudang’snorthernpartdisplaytheassemblagechlorite–phengite–amphibole–epidote–albite–quartz–titanite.Amphibolesarebluishmagnesioriebeckite/winchiteorpalegreenactinolite.PhengitehashighSi-contentsof3.4-3.5p.f.u.Basedonchlorite-phengite-quartzequilibria(Vidaletal.2005;Dubacqetal.2009)metamorphicconditionsof280-330°Cat0.5-0.8GPawerederived.Phengite’sSip.f.u.-isoplethscalculatedwithDOMINOpointtopres-sures of 0.7-0.8GPa at these temperatures.Discretedomains of stilpnomelane– calcite –phengite – chlorite – schist753011Apreservedrecordsofanearlymetamorphic stageat250-320°Cat0.5-0.9GPawhileotherdomainspoint toasubsequentoverprintat400-420°Cand0.5GPa.

Thesepetrologicaldatahighlightthehigh-pressureblueschisttogreenschistfaciesmetamorphicoverprintoftheWudangComplexduringthesubductionoftheleadingedgeoftheYangtzeplate.Thecentralpartwasburiedtogreaterdepthsalthoughthesamegeothermalgradientof~12°C/kmis,withinerrorsofgeobarometry,alsoappropriateforthelow-grademetamorphicnorthernpart.Ar/ArdatingofamphibolesandKwhitemicas(Mattaueretal.1985;Ratschbacheretal.2003)demonstratethatthishappenedintheLateTriassic.Duringsubduction,theWudangformedacontinuousportionofthedowngoing slab and, during exhumation,was delaminated and imbricated along south-directed thrust faults (Huang,1993).

Thecriticalassemblagestilpnomelane–albite–clinozoisiteinsample76032Dindicates,thattheexhumationofthecen-tralpartoccurredratherfast,asthestabilityofstilpnomelaneisindicativeforelevatedpressuresattemperaturesbelow~320°Cwhilethenorthernpart,atleastlocally,underwentamedium-pressureoverprintat~400°Cand0.5GPa.

REFERENCESDeCapitani, C.& Petrakakis, C. 2010: The computation of equilibrium assemblage diagramswith Theriak/Domino

software.Am.Mineral.95,1006-1016.Dubacq, B.,Vidal,O.&DeAndrade,V. 2009:Dehydrationof dioctahedral aluminousphyllosilicates: thermodynamic

modellingandimplicationsforthermobarometricestimates.Contrib.Mineral.Petrol.159,159-174.Huang,W.1993:Multiphasedeformation anddisplacementwithin abasement complexon a continentalmargin: the

WudangComplexintheQinlingOrogen,China.Tectonophysics224,305-326.Mattauer,M.,Matte,P.,Malavieille,J.,Tapponnier,P.,Maluski,H.,Xu,Z.Q.,Lu,Y.L.&Tang,Y.Q.1985:Tectonicsofthe

Qinlingbelt:build-upandevolutionofeasternAsia.Nature317,496–500.Ratschbacher,L.,Hacker,B.R.,Calvert,A.,Webb,L.E.,Grimmer,J.C.,McWilliams,M.,Ireland,T.,Dong,S.&Hu,J.2003:

Tectonics of the Qinling Belt (Central China): Tectonostratigraphy, geochronology, and deformation history.Tectonophysics366,1-53.

Vidal,O., Parra, T.&Vieillard, P. 2005: Thermodynamic properties of the Tschermak solid solution in Fe-chlorites:applicationtonaturalexamplesandpossibleroleofoxidation.Am.Mineral.90,347-358.

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Figure1.SummaryofthemetamorphicevolutionoftheWudangComplex

2.2

ReconstructionofNeogenepaleoelevationandpaleoclimaticconditionsoftheEuropeanAlpsandthecircum-Alpineregionbystableisotopeanalyses

BauerKerstin1,2,VennemannTorsten1,MulchAndreas2

1 Institut de Minéralogie et Géochimie, Anthropôle, Université de Lausanne, CH-1015 Lausanne, Switzerland ([email protected]) 2 Institut für Geologie, Leibniz Universität Hannover, Callinstr. 30, 30167 Hannover, Germany

Thestableisotopecompositionofoxygenandhydrogeninrainwatercorrelateswiththeairtemperatureandwiththealtitudeofprecipitation.Ifmeteoricwateristakenupintothestructureofmineralswithaknownwater-mineralfractio-nationfactor,itispossibletodetermineitsoriginald18OanddDvaluesandtherebytheformeraltitudeofprecipitationfrommeasurementsoftheisotopiccompositionofthehostmineralandknowledgeoftheambienttemperaturecondi-tions(e.g.Mulchetal.2004).

ThisstudywillapplythisapproachtoMioceneprecipitationinthecircum-Alpineregionviatheanalysesofhydrousclayminerals (e. g.Mulch& Chamberlain 2007). Previous paleontological and geochemical analyses of fossils (e.g. Janz&Vennemann2005,Kocsisetal.2009),fromthesamesamplestobeusedfortheclaymineralanalysiswillhelptoconstrainthepaleoclimaticconditionsthatexistedduringtheformationoftheclaysduringtheMiocene.ThecombinationofthemarinepaleoclimaticaswellasotherterrestrialfossilrecordswiththedetritalrecordoftheclaysmayallowestimatesonthechangesinelevationoftheAlpineregionduringorogenesis.

Measuredd18Ovaluesofbetween15.4and21.2‰,suggestthattheclayswereformedinthepresenceofmeteoricwaterthathadacomparableisotopiccompositiontothatofmodernwaterintheAlpineregionandattemperaturesofforma-tionthatcorrespondtotypicalsurfacetemperatures.

However,thetreatmentofthesamplematerialischallengingduetoitsextremelysmallgrainsizeandhygroscopicbeha-vior,whichmakesthedDvaluesdifficulttointerpret.Atrendtolowervaluesforsmallergrainsizefractionshintstopossiblecontaminationoramixof several components.XRDanalyses showthat the separatesdonotconsistofpuresmectite,butavaryingmixtureofsmectiteandilliteandalsomixed-layerminerals,whichmayalsofalsifythevaluesobtained.Furthertestsandexperimentstoinvestigatethesepossibilitiesareinprogress.

Furthermore,newsamplematerialwillbecollectedtofillthegapsbetweentheexistingdata.Drillcoresormoredetailedprofileswouldgivebetterconstraintsonthetemporalandspatialdistributionoftheresults.Inaddition,samplesfrom

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alteredvolcanicmaterialsuchasbentonitesmayprovidebetterabsoluteageconstraintscomparedtothepresentapproachofusingbiostratigraphyofindividuallyplacedsamplelocalities.Materialwithahighercontentofclaywillbeofadvantagetoachieveahigheryieldforthesamplepreparationandwillpossiblylimitsomeofthecontaminatingeffects.

AnotheraspectoftheresearchprojectwillinvolvetheinvestigationofrecentlyformedAlpinesoilsatdifferentaltitudes.The isotopecompositionof theclaysize fractionwillbe investigated incombinationwithprecipitationandsoilwaterisotopecompositioninordertostudythedirectinteractionofmeteoricwaterwiththemineralsduringsoilformation.

REFERENCESJanz,H.&Vennemann,T.W., 2005: Isotopic composition (O,C, Sr andNd) and trace element ratios (Sr/Ca,Mg/Ca) of

MiocenemarineandbrackishostracodsfromNorthAlpineforelanddeposits(GermanyandAustria)asindicatorsforpaleoclimate.Palaeogeography,Palaeoclimatology,Palaeoecology225(2005),216-247.

Kocsis, L.,Vennemann,T.W.,Hegner,E., Fontignie,D.,&Tütken,T., 2009:ConstraintsonMioceneoceanographyandclimate in theWestern andCentral Paratethys:O-, Sr-, andNd-isotope compositions ofmarine fish andmammalremains.

Palaeogeography,Palaeoclimatology,Palaeoecology271(2009),117-129.Mulch,A., Teyssier, C., Cosca,M.A.,Vanderhaeghe,O.,&Vennemann, T.W., 2004:Reconstructingpaleoelevation in

erodedorogens.Geology32,6(2004),525-528.Mulch,A.&ChamberlainC.P.,2007:StableIsotopePaleoaltimetryinOrogenicBelts–TheSilicateRecordinSurfaceand

CrustalGeologicalArchives.ReviewsinMineralogy&Geochemistry66(2007),89-118.

2.3

ZirconU/PbdatingoftheLateCarboniferousZervreilaOrthogneiss,AdulaNappe.

MattiaCavargna-Sani1,Jean-LucEpard1,FrançoisBussy2&AlexeyUlianov2

1 Institut de Géologie et Paléontologie, Université de Lausanne, Bâtiment Anthropole, 1015 Lausanne ([email protected])2 Institut de Minéralogie et Géochimie, Université de Lausanne, Bâtiment Anthropole, 1015 Lausanne

TheZervreilaOrthogneissisoneofthedominantlithologiesofthenorthernAdulaNappe(Jennyetal.1923).However,theageofmagmaticemplacementofthisrockwasneverdeterminedprecisely.Thisageisimportanttobetterunderstandthelithologies(lithostatigraphy)andthegeometryoftheAdulaNappe.

GeochemicaldatashowthattheprotolithoftheZervreilaOrthogneissisaSi-richgranite.Zirconsfromthisorthogneissformaveryhomogeneouspopulation. Inheritedcoresandevidencesofmetamorphicgrowthareabsent.AccordingtoPupinclassification(1980),thesearemainlyP-typezirconssimilartozirconsfoundinalkalinegranitesfromextensionaltectonicenvironments.WehavedatedthezirconsfromtheZervreilaOrthogneissbyLA-ICPMSusinganElementXRsec-tor-field instrument interfacedtoanUP-193excimerablationsystem.A5Hzrepetitionrateandanon-sampleenergydensityof2-2.4J/cm2wereappliedtominimisethelaserinducedfractionation.AGJ-1zirconwasusedasaprimarystan-dard.Analyseswereperformedonoscillatorymagmaticgrowthzonesrecognisableincathodoluminescenceimages.

SamplesdatedcomefromfourlocalitiesinthenorthernAdulaNappe:ValScaradra,Zervreila,andtwocloselysituatedoutcropsfromZapport.TheU/Pbagesofthesesamplesarelargelyconcordant;the206/238agevaluesare296.10(+2.90-1.80)Ma,291.20(+8.10-3.00)Ma,288.65(+3.25-4.75)and293.60(+3.90-2.00)Ma,respectively.Withintheanalyticalerror,thesefouragesareinterpretedtoresultfromthesamemagmaticeventandtocorrespondtotheintrusiontimeofagra-niticbody,probablyemplacedwithintheAdulaparagneissesinthelateVariscanpost-orogeniccontext.

REFERENCESJenny,H.,Frischknecht,G.&Kopp,J.1923:GeologiederAdula.Beitr.Geol.KarteSchweiz(N.F.)51,1-123.Pupin,J.P.1980:Zirconandgranitepetrology.ContributionstoMineralogyandPetrology73,207-220.

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2.4

Effectsofdeviatoricstressonnaturalfluidinclusionsinquartz:anexpe-rimentalstudy

DiamondLarrynW.,1TarantolaAlexandre1,StünitzHolger

1 Rock–Water Interaction Group, Institute of Geological Sciences, University of Bern, Baltzerstrasse 3, CH-3012 Bern, Switzerland ([email protected])2 Department of Geology, University of Tromsø, Dramsveien 201, 9037 Tromsø, Norway

Fluidinclusionsinquartzareknowntomodifytheirshapes,texturesanddensitiesduringsheardeformation.Modificationsofchemicalcompositionarealsosuspected.However,suchchangeshavenotbeenexperimentallydemonstrated, theirmechanismsremainunexplained,andnocriteriaareavailabletoassesswhetherdeformedinclusionspreserveinformati-ononpaleofluidpropertiesandpaleostressconditions.

Toaddresstheseissues,quartzcrystalscontainingnaturalCO2-H2O-NaClf luidinclusionshavebeenexperimentallysub-jectedtodeviatoricstressesof90–250MPaat700°Cand~600MPaconfiningpressure.Strainsofupto1%causethein-clusionstodevelopirregularshapes(Fig.1,2a)andtogeneratemicrocracksincrystallographicplanesorientedsubperpen-dicular to themajor compression axis,s1. The uniform alignment of themicrocracks imparts a planar fabric to thesamples(Fig.1b).Inclusionexpansionduetomicrocrackingreaches20%,producinglowfluiddensitiesthatbearnorela-tiontophysicalconditionsoutsidethesample.Nevertheless,thecompositionoftheprecursorinclusionsispreserved(Fig.2b).Themicrocrackshealandformswarmsoftinysatelliteinclusionswithawiderangeofdensities,thehighestreflec-tingthestressvalueofs1.Thesenewinclusions loseH2Oviadiffusion,therebypassively increasingtheirsaltandgascontents,andtriggeringplasticdeformationofthesurroundingquartzviaH2O-weakening.Consequently,thequartzsam-plesdeformplasticallyonlyindomainsoriginallyrichininclusions.

Thisstudyshowsthatf luidinclusionsdeformedbydeviatoricstressesmayrecordinformationonpaleostressesandonpre-deformationf luidcomposition,andthattheyplayakeyroleinfacilitatingcrystal-plasticdeformationofquartz.

Figure1.Summaryandnomenclatureofshapechangesaccompanying~1%plasticstrain.Viewlookingdowns1.

a

Figure2a.Shapechangesaccompanying~1%plasticstrain:Exampleviewlookingdowns1

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Figure2b.Shapechangesaccompanying~1%plasticstrain:Exampleviewlookingperpendiculartos1.

Figure3.Compositionalchangesaccompanying~1%plasticstrain.

REFERENCESDiamond, L.W., Tarantola,A.& Stünitz,H., 2010:Modification of f luid inclusions in quartz by deviatoric stress II:

Experimentally induced changes in inclusion volumeand composition.Contributions toMineralogy andPetrologyDOI10.1007/s00410-010-0510-6.

Tarantola,A.,Diamond, L.W.& Stünitz,H., 2010:Modification of f luid inclusions in quartz by deviatoric stress. I:Experimentallyinducedchangesininclusionshapesandmicrostructures.ContributionstoMineralogyandPetrologyDOI10.1007/s00410-010-0509-z.

2.5

U–PbgeochronologyofanorthogneissdiscoveredwithintheHP–LTmetamorphicrocksoftheIledeGroix,ArmoricanMassif,France

ElKorhAfifé1,SchmidtSusanneTh.1,BallèvreMichel2&BruguierOlivier3

Département de Minéralogie, Université de Genève, Rue des Maraîchers 13, CH-1205 Genève, Suisse ([email protected], [email protected])2 Géosciences Rennes (UMR CNRS 6118), Université de Rennes 1, Campus de Beaulieu, F-35042 Rennes Cedex, France ([email protected])3 Géosciences Montpellier (UMR CNRS 6250), Université de Montpellier 2, Place Eugène Bataillon, F-34095 Montpellier Cedex 05, France ([email protected])

Forthefirsttime,analbiticorthogneisshasbeenrecognisedanddatedwithintheHP–LTblueschistfaciesmetabasitesandmetapelitesoftheIledeGroix.Itispartoftheremnantsofanaccretionarycomplexformedaftersubductionandexhumationofanoceaniccrustand itssedimentarycover (Bernard-Griffithsetal.,1986).TheHP–LTevent (blueschist

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facies)isdatedat358–365Mawiththe40Ar/39Ar(phengite)andRb–Sr(wholerock,phengiteandepidote)methods(Bosseetal.,2005).Thealbiticorthogneissoccursas40cmthicklayerswithinHP-LTmetapelitesandiscomposedofanassemblageofalbiticplagioclase, perthitic porphyroclasts of K-feldspars, quartz, phengite, epidote rimmingmetamict allanite, and garnet.Accessorymineralsconsistoftitanite,apatiteandzircon.Themajorelementcompositioncorrespondstothatofperalu-minousleucogranites,characterisedbyveryhighcontentsofSiO2(75.5wt%),lowCaOcontents(1.7wt%)andhighA/CNKratios(1.5).The[FeOt/(FeOt+MgO)]ratioishigh(0.8).ThetraceelementcompositionoftheorthogneissdisplayshighLILE,ThandUcontents,MORB-likeHREEabundancesandmoderateNbandYvalues.Despitetheperaluminousorogenicsignature,thechemicalcompositionofthestudiedorthogneiss,aswellasthepresenceofaccessoryallanite,apatite,tita-niteandzirconindicateawithin-plateanorogenicoravolcanicarcorigin.TitaniteandzirconweredatedbyLA-ICPMS,attheUniversitiesofMontpellierandLausanne,respectively,bothusinganElementXRspectrometer.Titanite(40to200μm)wasanalysedin-situinthinsections.Zircons(25to100μmlong)wereextractedandseparatedfollowingtheconventionalmineralseparationproceduresusinggravimetricandmagneticme-thods.TitaniteandzirconU–PbdataarerepresentedtogetherinaTera-Wasserburgdiagram(Fig.1).Nocommonleadcorrectionwasapplied.ThedatadefineaConcordiainterceptat480.9±3.1Ma,withaMSWDof12,interpretedastheageofthemagmaticemplacementduringtheearlyOrdovician.Additionalzircongrainsyield lateNeoproterozoic (i.e.Cadomian)206Pb–238Uages[546.6–606.0Ma]. TitaniteandzirconU–PbagesindicatethatthefelsicmagmatismfromtheIledeGroixiscontemporaneouswiththegranitictorhyolitic,pre-orogenicplutonismwidelyrecognizedintheinternalzonesoftheVariscanbelt,relatedtotheOrdoviciancontinentalrifting.ThiseventledtotheopeningoftheRheicandGalicia-SouthernBrittanyoceans,andtothedetachmentofthemicrocontinentArmoricafromGondwana.Themagmaticprotolithprobablyinheriteditsspecificchemicalcompositionfromacombinationoforogenicandanoro-genicsignaturesduetopartialmeltingoftheCadomianbasementduringgraniteemplacementinacontinentalriftingenvironment.

Figure1.Tera–WasserburgplotsfortitaniteandzircongrainsfromorthogneissGROA115a.(a)Alldata,(b)titanites,(c)zircons.

REFERENCESBernard-Griffiths, J., Carpenter,M.S.N., Peucat, J.-J.& Jahn, B.M. (1986).Geochemical and isotopic characteristics of

blueschistfaciesrocksfromtheIledeGroix,ArmoricanMassif(northwestFrance).Lithos19,235–253.Bosse,V.,Feraud,G.,Ballèvre,M.,Peucat, J.-J.&Corsini,M. (2005).Rb-Srand 40Ar/39Arages inblueschists fromthe Ilede

Groix(ArmoricanMassif,France):Implicationsforclosuremechanismsinisotopicsystems.ChemicalGeology220,21–45.

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2.6

Pre-AlpinemetamorphismintheclassicalAlpinestaurolite-garnetschistofCampolungo

JörgHermann1,2&DanielaRubatto1,2

1 Research School of Earth Sciences, The Australian National University, AU-0200 Canberra ([email protected])2 Present Address: Institute of Mineralogy and Geochemistry, Université de Lausanne, Anthropole, CH-1015 Lausanne

TheCampolungoarea,Ticino,representsoneoftheclassicalareaswhereAlpinemetamorphism,structureandtectonicshavebeeninvestigated.Theareaexposesawell-preservedMesozoicstratigraphy(Bianconi,1971)rangingfrombasalquart-zitestodolomites(presumedTriassicdepositionage)toBündnerschiefer(presumedJurassicdepositionage).ThissequenceshowsaseriesofoverprintingAlpinestructures(Gruijc&Mancktelow,1996)andassociatedmetamorphismreachesam-phibolitefaciespeakconditions(~6.5kbaratthethermalpeakof~600°C;Todd&Engi,1997).,Staurolite-garnetschistsoutcropstratigraphicallybelowthequartzites.TheschistsdisplayacomparablestructuralandmetamorphicevolutiontotheMesozoicrocksandthushavebeeninterpretedaslatePaleozoicclasticsedimentsthatweremetamorphosedduringtheAlpineorogeny.

We investigated indetail staurolite-garnetschists inthevicinityof theCapannaLeit.Thesamplesconsistofphengite,quartzandfine-grainedgraphite,markingapenetrativefoliationthatisalsorefolded.Asecondgenerationofphengiteispresentintheaxialplanecleavageofthecrenulation.Garnetoccursasporphyroblasts,partlyovergrowingthefoliation.Staurolitealsoformspostkinematicporphyroblasts.Latebiotitef lakesoverprintthemainfoliation.Rutilecoresareover-grownbyilmenite,andaccessorytourmaline,monaziteandzirconaredispersedthroughoutthesamples.Especiallyingraphiterichrocks,monazitecontainsorientedgraphiteinclusionsprovidingevidencethatmonaziteformedsyntopost-kinematictothemainfoliation(Fig.1).

MonazitegrainswereseparatedforSHRIMPdatingfromtwostaurolite-garnetschists.Despiteitstexturalposition,mona-ziteconsistentlyyieldedpre-Alpineagesof~330Ma,correspondingtotheknownVariscanmetamorphism.NotraceofAlpine(~30Ma)metamorphismwasfoundinmonaziteinthesesamples.ThisindicatesthatatleastpartofthefoliationintherocksisnotofAlpineageandthatthestaurolite-garnetschistsrepresentacrystallinebasementtotheMesozoicsediments.

Amultistageevolutionisalsopreservedinthegarnet.WhereasMn,FeandMgelementalmapsdonotshowanyzoning,theCa-mapdisplaysastrongdiscontinuityseparatingalarge,zonedgarnetcorefromasmall,homogenousrim.Thetran-sitionischaracterizedbyahighlyirregularsurfacethatcrosscutpreviouszoningandisenrichedinCa.ItisimportanttonotethatgarnetinthenearbyBündnerschiefer(thatexperiencedonlyAlpinemetamorphism)donotshowanyofthesefeatures.

TraceelementprofilesacrossthegarnetdisplayaYandHREErichcorewithmarkedtraceelementdepletiontowardstheintermediategarnetzone,typicalofprogradegrowthzoning.Phosphorousincreasessteadilyfromcoretotheintermedi-atezone.Atthediscontinuity,visibleintheCamaps,YandHREEincreasebyafactorof5,indicatingresorptionofpre-existinggarnet.Intherim,YandHREEdecreasedrasticallyagain,whileP,aftershowingasignificantdropattheinter-face,increasestovaluesobservedintheintermediategarnetzone.WeinterprettheseobservationsastheAlpineprogadegrowthofagarnetrimonapreviously,partlyresorbed,Variscangarnet.Thegarnetcorecontainsinclusionsofchloritoidandstaurolite,whereasonlystaurolitewasfoundinthegarnetrim.Therefore,thepetrographicobservations,majorele-mentmappingandtraceelementprofilesingarnetcombinedwiththedatingofmonaziteindicatethattheinvestigatedmica-schistsatCampolungoexperiencedstaurolite-garnetgrademetamorphismduringVariscanaswellasduringAlpinemetamorphism.

REFERENCESBianconi, F.,1971.Geologiaepetrografiadella regionadelCampolungo.BeiträgezurGeologischenKartederSchweiz,

vol.142.Kümmerly&Frey,Bern.Grujic,D.,&Mancktelow,N.S.,1996.StructureofthenorthernMaggiaandLebendunNappes,CentralAlps,Switzerland.

EclogaeGeologicaeHelveticae89,461–504.Todd,C.S.,&Engi,M.1997.MetamorphicfieldgradientsintheCentralAlps.JournalofMetamorphicGeology,15,513-

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Figure1.Monazitecrystal(200µmlong)withinternalgraphitefoliationfromastaurolite-garnetschist.Theageofmonazitesinthis

sampleis~330Ma,indicatingthatpre-AlpinemetamorphismanddeformationispresentintheCampolungoarea.

2.7

Thermo-mechanicalreactivationoflockedcrystalmushes:melting-indu-cedinternalfracturationandassimilationprocessesinmagmas

HuberChristian1,BachmannOlivier2&DufekJosef1

1 School of Earth and Atmospheric Sciences, Georgia Institute Technology, Ferst drive 311, Atlanta, GA, USA ([email protected])2 Department of Earth and Space Science, University of Washington, Seattlle,

Thermalreactivationoflockedcrystalmushesintheuppercrustisafundamentalsteptowardstriggeringvolcanicerup-tionsofcrystal-richmagmas.Modelsofsuchreactivationeventsindicatethatpartialmeltingofthecrystallineframeworkisenergeticallycostlyandleadtoaveragecrystallinitiesthatarelowerthanthoseobservedinmanyeruptedcrystalmus-hes.Here,weshowthatinternaloverpressurizationofthemushinducedbysmallamountsofmelting(10-20%)breaksthecrystallineframeworkbymicrofracturationandallowsforefficientunlocking.Hence,thismelting-inducedoverpres-surization,enhancedbyadditionofgasinwetmagmaticsystems,playsanimportantroleingeneratingvolcanicdepositswithcrystal contents close to the rheological lock-up (~50vol%crystals)byaccelerating the incorporationofhighlycrystallinepartsofthemagmachamber(self-assimilation).Itcanalsoparticipateindisintegratingpiecesofcountryrockthatarecommonlyscavengedinmagmas,leadingtobulkassimilationofcrustallithologiesinshallowreservoirs.

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2.8

Theinfluenceofferric/ferrousironratiosinbulkandmineralsofblue-schistsfromtheInnerMakran(SEIran)onthermobarometricrecalculations

HunzikerDaniela1,CaddickMark2,ReusserEric2,BurgJean-Pierre&MüllerElisabeth3

1 Geological Institute, Structural Geology and Tectonics, ETH Zurich, Sonneggstrasse 5, NO E69, CH-8092 Zurich ([email protected])2 Institute for Mineralogy and Petrology, ETH Zurich, Clausiusstrasse 25, CH-8092 Zurich3 Electron Microscopy ETH Zurich (EMEZ), HP D11, CH-8093 Zurich

Toreconstructsubductionparameterslikedepthofburialandsubsequentexhumationthethermobarometricconditionsofrecrystallizationofblueschistfaciesrockshastobewellconstrained.Calculations andmodels involve charge balance-based assumptions concerning the Fe3+/Fe2+ ratio ofmineral phases.However,theseratiosarepoorlyknownformostminerals,especiallyforsodicamphiboles.

We approach the problemby studying the petrography, geochemistry and thermobarometry of scarcely studied blue-schistsintheInnerMakranofSoutheastIran.Comparingmetamorphicpressureandtemperatureconditionscalculatedwithdifferentferric/ferrousironratiosofbulkandmineralsillustratesthestronginfluenceofthisratio.RecalculationsusingthetruebulkFe3+/Fe2+ratiooftheMakranblueschistsmeasuredbycolorimetrictitrationandanestimatedvaluefrommineralparagenesesdifferlargely.Thisisprobablyduetoinaccurateamphibolemodels,whichtendtoconsideratoo lowferric/ferrous ironratio.Usingelectronenergy-lossspectroscopy (EELS)quantitativeanalysesofallparageneticmineralphaseswillbeanalyzedandcross-checkedwithmicro-X-rayabsorptionnear-edgestructure(XANES)analysisandMössbauerspectroscopy.

Theresultsenteredintoamphibolemodelswillimprovepressure/temperaturerecalculationsofblueschist-faciesandotheramphibole-bearingmetamorphicrocks.

2.9

Subvolcanicmafictointermediatedike-systems:contraintsonpost-plu-tonicactivity(S-Adamello,N-Italy)

HürlimannNiklaus1,MüntenerOthmar1&UlmerPeter2

1 Institute of Mineralogy and Geochemistry, Anthropole, CH-1015 Lausanne, Switzerland ([email protected])2 Institute of Geochemistry and Petrology, Clausiusstrasse 25, CH-8092 Zurich, Switzerland

Variousscalesofdikegeometriesprovidearecordofstrainduringtheiremplacement.Distinctdikegenerationsmightrecordstrain-evolutionthroughtime.Inaddition,dikerocksaregenerallyclosetoliquidcompositions,inparticularma-ficcompositions,relativetoplutonicrocks.Herewepresentfieldevidenceofstructuralrelationshipsandfirstpetrologi-calandgeochemicaldatathatcharacterizetheevolutionofpost-batholithsubvolcanicmagmaticactivityduringcoolingofaplutonic-suiteintheSouthernAdamellomassif(Italy).

At least threedifferentgenerationsofmafic to intermediatedikesofpicrobasaltic toandesiticcompositionpostdateasuccessionoflargevolumeplutonemplacement(Schalteggeretal.2009,HansmannandOberli1991,DelMoroetal.1985).Early,partiallydeformeddikegenerationsappeartoreflectmorelocalstrainwhereaslateronesreflectamuchmorere-gionalstrainpatternthatappearstobeindependentofinterplutonicandwallrockcontacts.Subverticaldikesarecharac-terizedbycomposite,multiplestagetexturesandareoftenphenocryst/xenocryst-richwhereassubhorizontal typesarerelatedtosimpleronestageorpulseemplacement.

Subhorizontaltypesshowawiderangeofphenocrystphasessuchasolivine,clinopyroxene,amphiboleandplagioclase.Evolvedphasessuchasallanite-epidote,titanite,apatiteandzirconaremainlyassociatedwithmorefelsiczonesorbandswithinthedikes.Plagioclaseinthesefelsiczonesshowsalargerangeofcompositionalvariation.Suchfelsiczonesappeartorepresentevolvedliquidsegregationsfromratherclosedsystemfractionation(equilibriumcrystallization).

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Bulkrockgeochemistryandpetrographyindicateanevolutiontomoreevolvedmagmastowardsyoungergenerationsandpulses.Particularlythelaterdikegenerationscarryvariableproportionsofxenocrysticmaterial.Majorandtraceelementconcentrationsofbulkrocksindicatethataphyricdikemarginsinsinglepulsesystemsdisplayamoreevolved‘hydraulichead’followedbyatrailingthatismoreprimitiveindicatedbyincreasingcontentsofMgO,Fe2O3,CrandNifromthedikemargintowardsthecenter.

Wewillpresentmajorandtraceelementsoftheaphyric-matrixobtainedbyLaser-Ablation-ICP-MS,todetermineactualliquidcompositionsandtotestequilibriumwithrespecttozonedphenocrysts.Wewillprovideconstraintsoncontamina-tionanditssourceswithquantitativeestimatesonxenocrystcontentinindividualsampleswithregardtodikesormagmapulsesthatshowlessornocontamination.Particularwellestablishedcompositionalzoningpatternsinclinopyroxene-phenocrystswillfurtherallowapplicationofrespectivegeospeedometerstoconstrainreservoirresidencetimeswithre-gardtocationinterdiffusion(Chakrabortyetal.2008).

REFERENCESChakraborty, S., Dohmen, R.,Mueller, T., Beaker,H.W.& TerHeege, J. 2008: Fe-Mg interdiffusion coefficients in

clinopyroxene:experimentaldeterminationsusingnanoscalefilms.AGU,FallMeeting2008,abstract#MR21C-04.DelMoro,A.,Pardini,G.,Quercioli,C.,Villa,I.M.&Callegari,E.1985:Rb/SrandK/ArchronologyofAdamellogranitoids,

SouthernAlps.MemoriedellaSocietàGeologicaItaliana,26,261-284.Hansmann,W.& Oberli F. 1991: Zircon inheritance in an igneous rock suite from the southernAdamello batholith

(ItalianAlps).ContributionstoMineralogyandPetrology,107,501-518.Schaltegger, U.,Brack,P.,Ovtcharova,M.,Peytcheva,I.,Schoene,B.,Stracke,A.&BargossiG.2009:Zirconandtitanite

recording1.5millionyearsofmagmaaccretion,crystallizationand initialcooling inacompositepluton (southernAdamellobatholith,northernItaly).EarthPlanetaryScienceLetters,286,108-218.

2.10

ThepigmentsofthemedievalpaintersinFribourg:InvestigationofatopqualitymuralpaintingfromtheCordeliersChurchinFribourg.

IldikoKatona&VincentSerneels

Department of Geosciences, University of Fribourg, Chemin du Musée 6, CH-1700 Fribourg ([email protected])

Duringthe80’s,thousandsoffragmentsofmuralpaintingdatingbacktothelatemedievalperiod(15thcenturyAD)werefoundduringrestorationworksinthechurchoftheCordeliersinFribourg.For25years,theyremainunexploitedattheArchaeologicalServiceofFribourguntiltheirextraordinaryestheticqualitywasrecognized.

Since2009,aninterdisciplinaryteamofresearchershasbeensetupandtheprojecthasbeensupportedbytheSNF.Itincludesthereconstructionoftheentirescene-20’000fragments-(S.Garnerie),thearthistorical(B.Pradervand,J.Bujard)andthetechnicalstudies(J.James,V.Serneels,I.Katona).Theaimofthisstudyistheidentificationofthematerials(pig-ments,binders,supports)andthedescriptionofthepaintingtechnique.

Chemical (XRF)andmineralogical (XRD)analysesareusedtogetherwithmicroscopicalobservationsofthesurfaceanddispersedpowdermicroscopyfortheidentificationofcomponents.Asthismajorworkofart isalreadyfragmented, itoffersonexceptionnalopportunityforthesystematicalsamplingofthewholepaintedlayerandtheproductionofnu-meroussmallpolishedsections.ThismakespossibletheuseofSEMasamajormethodofinvestigation.Ontheotherhand,theburialofthefragmentsunderthegroundinsidethechurchallowsaverygoodpreservationofthefragilepaintedlayer.

Themedievalartist,stillunidentified,wasusingalargevarietyofmineralpigments,includinghighqualityones,likeredcinnabar,blueazurite,artificialSn-Pbyellowandevengold.Histechniquewashighlysophisticatedwithpigmentsmix-turesfortheproductionofspecificshadesandsuperpositionoflayerstoobtaincomplexvisualeffects.Firstmineralogicalresultsonthismaterialwillbepresented.

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2.11

Combustionanalysisofameteoritedebris

KayaniSaheeb-Ahmed

National University of Sciences and Technology, H-12, Islamabad-44000, Pakistan ([email protected])

AmeteoriteablationdebrishasbeenidentifiednearvillageLehri(33°09’09”N;73°33’35”E)indistrictJhelum,PakistanbyKayani(2009).Inthisresearchstudy,totalcarboncontentofthemeteoritedebrishasbeendeterminedandthisabundancehasbeencomparedwithvaluesreportedinliteraturetoidentifytheoriginsoftheparentbodyofthismeteoritedebris.

Carbonisoneofthemostimportantelementsinnature.Itcanexistinmanystableformsandthechemicalstructureofcarbonaceousmatterdependsuponavailable environmental conditions.Theabundance, compositionand structureofcarboncanbeanalyzedtogatherinformationabouttheinitialformationprocessandfollowingenvironmentalchangestothecarbonaceousmatter(Muraeetal.1993).Incarbonrichchondrites(stonymeteorites),carbonaceousmatterhasbeenidentifiedasgraphite,amorphous,kerogen-like,insomecasesdiamond,andmostlyasastructurallyunclearinsolublehighmolecularorganiccompound.Inironandstony-ironmeteorites,carbonisfoundasgraphiteorlessorderedgraphiticmatter(Muraeetal.1993;Swartetal.1983;Amarietal.1990).

In lightoftheabove, itseemsthatcarbonabundancecanserveasausefulclueto identifythenatureandoriginofaparticularmeteorite.Furthermoreitcanalsobeusedtodetectalterationsinthestructureoftheoriginalmatter(ofthemeteorite)dueto impactsorcollisionsetc.Forthemeteoritedebrisunderstudy,throughXRDanalysismagnetiteandwustitehavebeendetectedaspredominantironphases(Kayani2009).Presenceofwustiteshowsareducingenvironmentwhichmayhaveexistedeitherduetocollisionoftheparentbodywithanothercelestialobjectorduetohighpressureandtemperaturecausedbyresistancefromtheatmosphereofearth.Asthemeteoritedebrishasbeenfoundlyingoverthesiteinformofsmallstones,itseemsonentryintoearth’satmosphere,theparentmeteoroidsuccumbedtoincreasin-glyhighpressureandtemperatureandatacertainheightexplodedintoinnumerablesmallpiecesthatcametorestonthisparticularsite.Thiskindofbehavioristypicallyobservedwithchondritesastheyaremorevulnerabletohighpres-sureandtemperatureeffectsduetotheircompositionandstructure.

Inordertodeterminetheabundanceofcarbonandsulphurinthemeteoritedebris,aspecimenwastestedthroughcom-bustion analysis using the facilities at Petroleum Geochemistry Laboratory of Hydrocarbon Development Institute ofPakistaninIslamabad.Incombustionanalysisofmeteorites,carbonisreleasedoverthreedifferentheatingranges.Recentcontaminantsaredetectedbelow500°Cwhileweatheringproducts(i.e.carbonates)decomposearound1000°C.Thespal-logeniccomponents(frommetalsandsilicates)areidentifiedduringmelting.Heatingupto1000°Cisusedtodeterminetheweatheringagewhereasthemeltisanalyzedtoestablishaterrestrialorresidenceageforthemeteorite.Thetestingresultsare:Carbon0.43wt%andSulphur0.04wt%.

Thecarbonabundanceforthismeteoritedebrisisinconformitywithmediancarbonabundancevalueforenstatitechon-drites(i.e.0.4wt%)asreportedbyMooreandLewis(1965).ThiscarbonvalueandtheelementalcompositiondeterminedthroughXRFanalysisbyKayani(2009)supportstheideathattheparentmeteoroidbodyofthisdebrismayhavebeenanenstatitechondrite.Enstatitechondriteshaveahighironcontent(upto30wt%)andcontainamagnesium-siliconmineralenstatite(Mg2Si2O6).ThesiliconandmagnesiumabundancevaluesdetectedthroughXRFanalysisare3.93wt%and0.342wt%respectively(Kayani2009).Theincreasedrelativeabundanceofiron(56.28wt%)inthemeteoritedebrisisattributedtoablationeffectsexperiencedbytheparentmeteoroidbodyonitsentryintoearth’satmosphereanditssubsequentex-plosivedisintegrationintosmallmeteorites.Thismeteoroidmayberelatedtoaprimitiveundifferentiatedparentbodyoranasteroid.Suchasteroidsrepresenttheearliestrockybodiesthatoriginatedwithinthesolarsystem.Mostoftheseas-teroidsf loataroundthesunwithintheorbitsofMarsandJupiter(thesocalledasteroidbelt).

Onthebasisoftheanalysisincludedabove,themeteoritedebrisisidentifiedasthatofanenstatitechondrite.Theparentbodyofthismeteoritedebrismayhaveoriginatedfromtheasteroidbelt.Itmayhavebeenhurled(asaresultofacollisi-onwithaneighboringcelestialobject)intoatrajectorythatultimatelybroughtitintocloseproximityofearthandwasfinallypulleddownbyearth’sgravitycausingittocrashonthisparticularsite.

REFERENCESAmari,S.,Anders,E.,Virag,A.&Zinner,E.1990:Interstellargraphiteinmeteorites.Nature,345,238-240.Kayani, SA. 2009:Using combinedXRD-XRF analysis to identifymeteorite ablation debris. In: Proceedings of IEEE

InternationalConferenceonEmergingTechnologies,Islamabad,October19-20,219-220.Moore,C.&Lewis,C.1965:Carbonabundancesinchondriticmeteorites.Science,149,317-317.Murae,T.,Kagi,H.&Masuda,A.1993:Structureandchemistryofcarboninmeteorites.In:PrimitiveSolarNebulaand

OriginofPlanets(Ed.byOya,H.).Tokyo:TerraScientificPublishingCompany.Swart,P.,Grady,M.,Pillinger,C.,Lewis,R.&Anders,E.1983:Interstellarcarboninmeteorites.Science,220,406-410.

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2.12

NatureandTempoofthePETM(Paleocene-Eocenethermalmaximum)events,newinsightsfromtheGSSPDababyiasection(Luxor,Egypt).

HassanM.Khozyem1,ThierryAdatte1,AbdelAzizTantawy2,JorgeE.Spangenberg3,GertaKeller4&KarlFöllmi1

1 Institut de Géologie et de Paléontologie (IGP), Université de Lausanne. [email protected] Department of Geology, South Valley University, Aswan 81528, Egypt.3 Institut de Minéralogie et Géochimie (IMG), Université de Lausanne.4 Department of Geosciences, Princeton University, Guyot Hall, Princeton, NJ 08544, USA

ThePaleocene-EoceneThermalMaximumGSSPhavebeen carefully selectedbyThe InternationalUnionofGeologicalSciences(IUGS)locatedatthebaseofacharacteristiclithologicsuccession(theDababiyaQuarryBeds)thatoccursinthelowerpartoftheEsnaShale,awellknownformationthatoutcropsextensivelythroughoutEgypt.Thisselectionwasbasedon: (1) theorganiccarbon isotopeexcursion (CIE) , locatedat thebaseofBed1of theDababyiaQuarryBedsof theElMahmiyaMemberintheEsnaFormation.(2)themassextinctionofabyssalandbathyalbenthicforaminifera(Stensioinabeccariiformismicrofauna),whichisreflectedatshallowerdepthsbyaminorevent;(3)thetransientoccurrenceoftaxaamongtheplanktonicforaminifera(Acarininaafricana,A.sibaiyaensis,Morozovellaallisonensis)duringthe∂13Cexcur-sion;(4)thetransientoccurrenceoftheRhomboasterspp.–Discoasteraraneus(RD)assemblage;and(5)anacmeofthedinoflagellateApectodiniumcomplex.TheGSSP-definedPaleocene/Eoceneboundaryisapproximately0.8myolderthanthebaseofthestandardEoceneSeriesasdefinedbytheYpresianStageinepicontinentalnorthwesternEurope(Aubry,M.-Petal.,2007).

High-resolutionsamplinghasbeenachievedfromtwosectionslocatedattheleftandrightsideoftheoriginalDababiyaGSSP.62samplesfromtheleftsidesectionand42samplesfromtherightsidesectionhavebeensubjectedtomicropale-ontological(nannofossils),sedimentological,mineralogicalandgeochemicalanalysisinordertoreconstructthepaleoen-vironmentalconditionsandclimaticchangesoccurringduringthePETM.Preliminaryfieldwork,sedimentologicalandstableisotopesdatasuggestthattheDababiyaGSSPsectionhasbeendepositedinasmallchannelstructurewhichcanbetracedover200m,withthebasalunitsaandb(Aubryetal.,2005)thinningtowardstheedgesoftheoutcropandfinallydisappearing. ThePaleocene-EoceneGSSP isconsequentlyonlycompleteovera2-3meterswidth, inthecenterof theoutcrop.Geochemically,(1)bothorganicandbulkrockcarbonisotopesshowalong-termgradualdecreasingandreachmaximumnegativevaluesatthemidofbed.2,(2)asevereandpersistentdecreaseind15Norgto~0‰,(3)SharpdecreaseinproductivityattheCIEintervalfollowedbyasignificant increaseuptotheendofthePETM, (4)AchangeinredoxconditionfromoxicbelowthePETMtoanoxicconditionsinthelowermostPETM,followedbynormaloxicconditions,(5)Amaximumhumidity(kaolinitepeak)coincidingwiththebaseofthePETM.Despite,thelackoflateralcontinuity,theDababiyaGSSPisoneofthemostcompletePETMsectionandrevealsinterestinganduniquefeaturesthatmaybecrucialforabetterunderstandingofthePETMevents.

2.13

NewisotopedatafromtheLateCretaceousandPaleogenephosphatebedsoftheGafsaBasin,Tunisia

KocsisLászló1,OunisAnouar2,ChaabaniFredj2&NailiSalahMohamed3

1 Institut de Minéralogie et Géochimie, Faculté des Géosciences et Environnement, Université de Lausanne, Switzerland2 Laboratoire des Ressources Minérales et Environnement, Faculté des Sciences de Tunis, Université de Tunis El Manar, Tunisia3 Compagnie de Phosphate de Gafsa, Direction de Géologie, Métlaoui, Tunisia

DuringtheLateCretaceousandPaleogeneTunisiawaslocatedinthesouthernmarginofTethysanditwasapartofthemainTethyangiantphosphoritebelt.AtthisperiodTethyanwaterscoveredmostoftheTunisianlandmassandonlysomeareasliketheDjeffaraandKasserineislandsemerged.BetweentheseislandslocatedtheintracratonicGafsaBasinthatwasconnectedtotheopenseawestwardandsometimeswaterexchangeoccurredintheeastthroughtheChamsiPass(Fig.1).SedimentationintheGafsaBasinwasconductedinasemi-closedsea,whereinnerneriticandcoastalenvironmentalter-nated(e.g.Chaabani,1995,Zaïeretal.,1998).PhosphatebedsoccurredfirstontheHardGroundoftheAbiodFormationintheEarlyMaastrichtian,wherethelayerscanreachlocallyonemeterinthickness,whilelater,duringthePaleocene-EarlyEocenemoremassiveandeconomicallyimportantphosphoritesweredepositedinthearea(ChouabineFormation).

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Thefirstdetailedstable isotopestudyof thephosphateremains (sharkteethandcoprolites) fromtheGafsaBasinwasconductedbyOunisetal.(2008).Thecarbonisotopeanalysesresultedinapronouncednegativecarbonisotopeexcursion(CIE)of3-4‰atthelimitofUnit-CandUnit-DoftheChouabineFormation,whichwasidentifiedintwodifferentsectionsandintwodifferentarchives(Fig.1).Initially,thereforethisCIEwasproposedtomarkthePaleocene-Eocene(P/E)bound-aryinthephosphateseries.

Theoxygenisotopiccompositionsofthefossilsindicateastablewarm,tropicalclimateduringthedepositionofthephos-phatelayers.AttheP/Eboundary,howeveraglobalhyperthermalevent(PETM–PaleoceneEoceneThermalEvent)occur-redreflectedbyanegativeoxygenisotopeshiftinbenthicforaminiferarecord(e.g.Zachosetal.2001).TheabsenceofanythermalanomalyatthePETMintheGafsasectionswasexplainedbythetropicalpositionandtheshallow,semi-closedconditionoftheGafsaBasin(Ounisetal.,2008).Howeverwhetherthisprecedingresultisonlyduetothisspeciallocalconditionorratheraglobalphenomenonatlowlatitudesisnotutterlyclear.

Further investigation, therefore isnecessary focusingon theconnectionof theGafsaBasinwith theglobalocean, thepossibleeffectsofdiageneticalprocessesandtheverificationofwideroccurrenceofCIEintheregion.Henceotherisoto-pesystemssuchasSrandNdhavebeeninvolvedandappliedforthesamesamplesuitspreviouslyinvestigatedintheAlima and Bliji Mountains (Ounis et al., 2008). In addition, shark teeth from the different phosphate layers of theChouabineandMétlaouiFormationsintheKefEddourregion(Métlaoui)werecollectedandanalyzedforSrisotopicratios.

The87Sr/86SrratiosarewidelyintheexpectedrangeoftheLateCretaceousandPaleocene-Eoceneopenseawaterhowevertheyounger samples showmorepronounceddeviations from theglobal Sr-evolution curve.TheeNd valuesof the fewsampleanalyzedarequitevariableandtheyvaryfrom-8.8to-10.7.Thesepreliminarydataindicateeitherenhancedcon-tinentalreworkingorincreasedinfluenceofearlydiageneticf luidonthesampleswhichismostpossiblyrelatingtothegradualclosuringofthebasinduringthePaleogene.

Forfurtherinvestigatingthesubject,intheKefEddourregionadetailedsectionoftheChouabineFormationweresamp-ledfocusingnotonlythephosphatebuttheintercalatedmarlsandcarbonatelayersespeciallyacrossthesupposedP/Eboundary.Bulksediment,totalorganicmatter,phosphateremainsandforaminifersaretheinitialtargetsforstableisoto-peanalysescriticaltotheP/Eboundary.

Figure1.PalaeogeographicalmapofthestudiedGafsaBasininTunisiaandtheobtainedoxygenandcarbonisotopedistributionsalong

twoPaleocene–EocenesequencesintheChouabineFormation(Ounisetal.,2008).NotethenegativeCIEatthelimitofUnit-Cand

Unit-D,butnovariationintheoxygenisotoperecord.

REFERENCESChaabani,F.,1995.DynamiquedelapartieorientaledubassindeGafsaauCrétacéetauPaléogène:Etudeminéralogique

etgéochimiquedelasériephosphatéeEocène,Tunisieméridionale.ThèseDoc.Etat.Univ.TunisII.Tunisie.Ounis,A.,Kocsis, L.,Chaabani, F.&PfeiferH.-R. 2008:Rare earthelementand stable isotopegeochemistry (d13Cand

d18O)ofphosphoritedepositsintheGafsaBasin,Tunisia.Palaeogeogr.Palaeoclimatol.Palaeoecol.,268,1–18.Zachos,J.,Pagani,M.,Sloan,L.,Thomas,E.&Billups,K.2001:Trends,rhythms,andaberrationsinglobalclimate65Ma

topresent.Science292,686–693.Zaïer,A., Beji-Sassi,A., Sassi, S.&Moody, R.T.J. 1998: Basin evolution anddeposition during the Early Paleocene in

Tunisia.In:Macgregor,D.S.,Moody,R.T.J.andClark-Lowes,D.D.(Eds.),1998.PetroleumGeologyofNorthAfrica.Geol.Soc.LondonSpec.Publ.132,pp.375–393.

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2.14

GeochemicalandmineralogicalexaminationsofromancruciblesfromAutun(France)

DanielaKönig&VincentSerneels

Department of Geosciences, University of Fribourg, Chemin du Musée 6, CH-1700 Fribourg ([email protected])

TheinvestigatedcruciblefragmentsarisefromanarchaeologicalexcavationofthesiteoftheLycéemilitaireinAutun(France).DuringtheexcavationofalargecraftsmanquarterattheRomantownofAutun,severalhundredkilosofcru-ciblefragmentshavebeencollected.Thereareobviousevidencesforfoundryworkbuttheproductionofcopper-basedalloys(Zn,Sn,Pb)isalsosupposable.ThearchaeologicalsiteisdatedtotheGallo-Romanperiod(Chardron-Picault&Pernot,1999).

Thisstudyaimstospecifythestructureoftheceramicstoidentifytherawmaterialanddescribethetechnologyofpro-duction.Forthis,usedanalyticalmethodscompriseopticalmicroscopy,SEMandSEM-EDXanalysesonwallcross-sections,X-raydiffractionanalyses(XRD)fromdifferentiablepartsoftheinnerwalllayeraswellasX-rayf luorescencespectroscopy(XRF)onthedifferentlayersofthecrucibles.

Ingeneral,thecruciblesshowamultilayeredwallstructure,whicharemadeupoftwotothreelayersofdifferentceramicmaterials.Eachlayerpossessesdistinctthicknessesandfabriccharacteristics.Thefirst(outer)andthesecond(inner)lay-er,whicharepresentinallcruciblesareopticallydistinguishablebythedifferingcolourandtheglass-matrixcomposition.Thesefeaturessupposemajormineralogicalheterogeneitiesbetweensinglelayersandindividualfragments.Aninnermost(third)layer,whichismissinginsomeoftheinvestigatedfragments,isprobableakindofinnerprotectinglayer.Thefa-bricisinfluencedbytwomoreimportantfactors.Firstly,thestronggradientoftemperaturebetweentheinnerandtheouterpartarebasedonthehighexternalfieriness.Secondly,thefabricisinfluencedbyinteractionbetweentheinnermetalliccharge,theceramicandthecontributiongasesfromoutside.

Thefirstresultsshowremarkabledifferencesbetweenthetwomainlayers.The inner layer ischaracterisedbyahighcontentofmullite,low-cristobalite,quartzandinsomecasesorthoclase,whereasthelow-cristobaliteisoftenillcrystal-lised.Therefore,firingtemperaturesareproposedtohavereachedapproximately1100°Cto1300°C.Incontrasttheouterlayerisdominatedbyahighercontentofmullitebearingglass.Additionally,somesamplescontainsecondaryanalcimeinthefirstlayer,whichwasformedduringtheburialstage.XRFanalysisdocumentsatentimeshigherCaOconcentrati-oninthefirst(outer)layerasinthesecond(inner)one.ThesporadicallyoccurringthirdlayerhasalsoadifferingCaOconcentration,whichishigherthantheconcentrationinthesecond(inner)one.Thisfeaturecouldbeafirsthintofdif-ferentsourcematerialsforthesinglelayers.

REFERENCESChardron-Picault, P.& Pernot,M. (1999): Un quartier antique d’artisanatmétallurgique àAutun - Le site du Lycée

militaire.Paris:MSH,320p.

2.15

FluidboilingandmixingduringlateststageorogenicgoldmineralizationatBrusson,NWItalianAlps

LambrechtGlenn1,DiamondLarryn1

1 Rock–Water Interaction Group, Institute of Geological Sciences, University of Bern, Switzerland ([email protected])

Weareinvestigatingf luidinclusionsinhydrothermalquartz-carbonate-sulphideveinsfromtheabandonedFeniliaMineatBrusson,northwesternItalianAlps.StudiedquartzsamplescontainearlyprimaryandpseudosecondaryinclusionsthatcanbeapproximatedbytheCO2–H2O–NaClsystem.Twotypesareobserved(Fig.1):first,abundantlow–XCO2LaqLcarVin-clusionsthathomogenizetoliquidat~230°Candhaveanaqueoussalinityof3.7mass%NaClequiv.;second,high–XCO2LaqLcarinclusionswithsimilarhomogenizationbehaviourandanaqueoussalinityof2.2mass%NaClequiv.Thetwocontras-

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tinginclusiontypesweredescribedbyDiamond(1990)andinterpretedtohaveformedduringboiling(phaseseparationinto“vapour”and“liquid”)ofthelow–XCO2-typeore-bearingsolution.Newcharge-contrastimaginghasrevealedfineovergrowthsofquartzonthemain-stagecrystals(quartzzone3inFig.2c).Thesehostlate-primaryinclusionassemblages,whichconsistofrarelow–XCO2LaqLcarVinclusions(identicaltothosede-scribedabove)coexistingwithabundantLaqVinclusions.Thelatterwerepreviouslyunknownatthisdeposit.Theircarbo-nicphaseshavevariablevolumefractions[j(car)]rangingfrom0.075to0.47(±4%)(Fig.1a),which,alongwithelementpartitioningdata,isdiagnosticofboiling.Theseinclusionshomogenizeat³180°CviathetransitionLaqV→Laq.

RamananalysisrevealedCO2,CH4andN2withinthecarbo-nicphasesofallLaqVinclusions,butthemolarratiosofthegasesvarysystematically.InFig.1btheseanalysesrevealalineararraystretchingfromcompositionsclosetothoseoflow–XCO2 LaqLcarV and high–XCO2 LaqLcar inclusions (end-memberno.1inFig.1)tocompositionsofabout4.4mol.%CO2,91.4mol.%N2and4.2mol.%CH4(end-memberno.2inFig.1).

Figure1.(a)Relationshipbetweenvolumefractionofthecarbonic

phase [j (car)] and mole fraction of N2 in the carbonic phase

[XN2(car)]and(b)molarcompositionofthecarbonicphaseinLaqV,

low–XCO2 LaqLcarV, and high–XCO2 LaqLcar inclusions from quartz-

veinsampleshostedbydifferenttypesofwallrock.

Theliquidend-members1,2and2baremutuallymiscibleattheentrapmenttemperatureofthelow–XCO2liquid,230°C.Therefore,thelinearcompositionaltrendofthelateprimaryLaqVinclusionsinFig.1bcanbeinterpretedasamixingline.Thus,itappearsthatboilingandmixingoccurredsimultaneouslyintheveinsystemduringprecipitationofquartzzone3(Fig.2c).

Figure2.(a)Photographofquartzcrystalwithfreegolddepositedonthesurface.(b)SEMcharge-contrastimageofapolishedsection

throughthiscrystal.(c)Schematicinterpretationofthecharge-contrastimageinb.Seetextforfurtherdetails.

ThequartzsampleinFig.2exhibitstwogenerationsofgold:smallinclusionswithinalategrowthzone(Earlygoldinzone2,Fig.2c);andfreegoldmostlyoverlyingtheoutercrystalsurface(Lategold,Fig.2c).Charge-contrastimagingrevealsthatthislategoldisyoungerthanthefinecrystalgrowthzone3(Fig.2c)thathoststhelateprimaryLaqVinclusionassembla-ges.Thelategoldisalsoindirectcontact,andthereforecoeval,withhealedfractures(zoneno.4inFig.2c)thathostasecondaryassemblageofvariable–XCO2inclusions(includingbothlow–XCO2LaqLcarVandhigh–XCO2LaqLcartypes).These

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newtemporalandcompositionaldeductionsareusedtoreconstructthehistoryofquartzgrowthintheFeniliavein:First,alow–XCO2-typecarbonicliquidformsmain-stagequartz(zone1inFig.2c)andalterstheadjacentwallrock.Subsequentsimultaneousprecipitationofgoldandquartzispresumablytriggeredbycoolingorbywall-rockreactions.Progressivecoolingandreductioninf luidpressureowingtoon-goingupliftoftheWesternAlpsinducesboilingofthemain-stagef luid(Diamond,1990).Poref luidfromthewallrockssimultaneouslyseepsintotheopenvein,whereitmixeswithboilingcarbonicf luid.AtthismomentthelateprimaryLaqVinclusionsaretrapped (zone3 inFig.2c).Finally,anewpulseofboiling,ore-bearingcarbonicf luidenterstheminelevel,fracturingtheexistingquartzcrystalsanddepositingthelategoldontopofthem(zone4inFig.2c).Withoutanyevidenceforwall-rockporewatersatthisstage,itseemsmostlikelythatpartitioningofgold-complexingligands (aqueousHS–andH2S)fromtheliquidintothecarbonicvapourtriggereddepositionofthelategold.

REFERENCESDiamond,L.W.1990:FluidinclusionevidenceforP-V-T-Xevolutionofhydrothermalsolutionsinlate-alpinegold-quartz

veinsatBrusson,Val-d’Ayas,NorthwestItalianAlps.AmericanJournalofScience,290,912-958.

2.16

KilnfurnituresfromthefaiencemanufactureofGranges-le-Bourg(HauteSaône,France):contrastingrecipes

MaggettiMarino1,MorinDenis2,SerneelsVincent1,NeururerChristoph1

1 Department of Geosciences, Mineralogy and Petrography, University of Fribourg, CH-1700 Fribourg ([email protected])2 CNRS, TRACES - UMR 5608, Université de Toulouse, F-31058 Tolouse

Duringarchaeologicalexcavationsofthebrickworks(16th-19thc.)fromGranges-le-Bourg(Morin&Morin-Hamon2004),faiencewastewasfoundfromanunknownlate18th/early19thc.production.InGranges-le-Bourg,coarse,aswellasfineceramicwasthereforeproducedsimultaneously.Archaeometricanalysisincluded35samplesofkilnfurnitureortechnicalceramic(firingplates,saggars,spacers,props,wads),5bricksandtilesand7claysinordertostudythechemical-mine-ralogicalcompositionoftheseobjects.Analyticaltechniqueswereopticalmicroscopy,X-rayf luorescence,X-raydiffractionandscanningelectronmicroscopy,coupledtoanenergy-dispersiveX-rayspectrometer.

Afirstgroupofkilnfurniture(firingplates,saggarsandprops)is,astobeexpected,calcium-andmagnesium-poor,wellsuitedtosupporthighfiringtemperaturesaswellasseveralfiringcycles.Thecoarseceramic(bricks&tiles)hasaniden-ticalchemicalcomposition.Saggarsandbricksaregrog-tempered.Thesecondgroupofspacersandwadsiscalcium-andmagnesium-rich(beween5-10wt.%CaOresp.MgO),matchingthechemicalcompositionofthefaienceproduction.Theancientpottersobviouslyusedtworecipesforthekilnfurniture:thebrick&tilerecipeandthefaiencepasterecipe.Theuseofanonrefractorypasteforthespacersandwadsispuzzling.Ceramicobjectswithsuchhighf lux(CaO,MgO)willmeltaround1100oC-theyarenotverywellsuitedtoresisthighfiringtemperaturesofafaiencekiln,nortosupportmanyfiringcycles.Weretheseobjectsusedonlyonce?LocalTriassic(Anisian)marlscontainmuchdolomiteandarechemicallysimilartotheHigh-Mggroup.Asshownbyverticalprofilesoftworawmaterialsoutcrops,thereisadecarbonatisationtowardsthesurface.ThetoplayerscorrespondchemicallywelltotheMgO-poorobjects.Thepottersusedsuchlocalrawmaterialandnotimported,specificrefractoryclays.Acoatingofeithertinglaze(withsignificantlylesstinoxidethanthefaiencepieces)orleadglazehasbeenappliedtotheinteriorofthesaggars.Fortheseobjects,asmallglaze-ceramicbodyinterfacehasbeenobservedonlyfortheleadglaze.Theabsenceofanysignificantreactionzoneindicatesthattheglazesuspensionwasappliedonalready(biscuit)firedsaggars.

REFERENCEMorin,D.,& Morin-HamonH. J. 2004: La tuilerie-faïencerie deGranges-le-Bourg, Bulletin de la sociöté d’Histoire et

d’Archéologiedel’ArrondissementdeLure,23,94-104.

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2.17

ThefaiencemanufactureLeBoisd’Épense(North-easternFrance,18/19thcentury)

MaggettiMarino1,RosenJean2,SerneelsVincent1,NeururerChristoph1

1 Department of Geosciences, Mineralogy and Petrography, University of Fribourg, CH-1700 Fribourg ([email protected])2 DR CNRS, UMR 5594, Faculté des Sciences, Université de Dijon, F-21000 Dijon

TheFrenchfactoryLeBoisd’Epensewasanimportanttin-glazepotteryproductionsiteintheyears1735-1742and1764-1848,withalmost200workersatthetopofitsactivity.Wepresenttheanalyticalresultsfor56faiences(=tin-opacifiedleadglazedearthenware),28samplesoftechnicalceramic(saggarsandspacers)and6localclays.Analyticaltechniqueswereopticalmicroscopy,X-rayf luorescence(XRF),X-raydiffraction(XRD)andscanningelectronmicroscopy,coupledtoanenergy-dispersiveX-rayspectrometer(EDS).

AsshownbyXRFanalysis,thefaienceisveryhomogeneousandhasatypicalcalcareousfaiencebody(16-24wt.%CaO).Nochemicaldifferencecanbeevidencedbetweenthebiscuitsandthefaienceswitha“grandfeu”oranenameldecorati-on.TheproductsfromthissitecaneasilybedistinguishedfromtheactuallyknownFrenchfaiencereferencegroups.Thespacersweremadefromthesamepasteasthefaience,butthesaggarswithaimportedrefractoryclay,richinAl2O3.Forthe faience body, amixing of two local clays has been reported in a paper from1877.However, the prospected localCretaceous(MiddleAlbian)claysneverexceed12wt.%CaO.AnadditionofaCaO-richmaterialisundoubtedlynecessaryto reach the 16-24wt.%CaO of the faience. This is not a localmarl, butmost probably a very pure chalk from theChampagne.FiringtemperatureswereinferredbyXRDandlie<950°Cforthebiscuitsandbetween950-1050°Cfortheglazedpieces, indicatinga twochamberedkiln.Thequalityof the tinglaze is ingeneralgood, showingrare roundedquartzcrystals,very fewnewlycrystallizedphases (K-feldspars,cristobalite?)andbubbles.Contrasting, thecassiteritecrystalsareheterogeneouslydispersed,formingclusters.Theabsenceofanyglaze-bodyinterfaceisconsistentwiththeapplicationoftheliquidglazetoanalreadyfiredbody.Areameasurementsshowthatalltinopacifiedglazescanbeclas-sifiedasSiO2-PbOglazes(~80wt.%)containingabout9wt.%SnO2,withotheroxidesinconcentrations<5wt.%.Spotanalysesoftheglassmatrixindicateamuchlowertinoxideamountofabout2wt.%ascomparedtotheareameasurements.

2.18

Forensicgeology:characterisationoflightelementstableisotopesinsoilsamplesoftheSwissPlateau

MarolfAndré1,VennemannTorsten1&BonzonJeanne2

1 Institut de minéralogie et géochimie, Université de Lausanne, Bâtiment Anthropole, CH-1015 Lausanne ([email protected])2 Musée cantonal de géologie, Université de Lausanne, Bâtiment Anthropole, CH-1015 Lausanne

ThepurposeofthisworkistocharacterisesoilsamplesfromtheSwissPlateaufortheirstablecarbonandoxygenisotopecompositionsasabasisforforensicandgeologicalresearch.FivesamplinglocationswerechoseninthecantonsofGeneva,Vaud,FribourgandValais,andsixinthecantonofZurich.Thecoordinatesofthelatterlocationshavebeentakenfromrealcrimescenes (anonymised).Fourteensamplesperlocationwerecollectedforall localitiesexceptforthecantonofZurichwheresixsamplesperlocationwerechosen,followingaregularpatternforalllocalities.AllthesoilsampleswerecharacterisedfortheircarbonandoxygenisotopiccompositionviaIsotopeRatioMassSpectrometry(IRMS).Organiccom-poundshavebeenremovedandcarbonatesandsilicatesanalysedseparatelywithaGasBenchII,respectivelyaCO2-laserbasedextractionline,bothlinkedtoanIRMS.

TheresultsindicatethatcarbonandoxygenisotopesareapromisingtooltoinvestigatevariationsinsoilsfromtheSwissPlateau,butdistinguishingbetweenlocationsinthesameregionisstillchallenging.Despitethesedifficulties,threemajordomainscanbeclearlydistinguishedandthedatashowsthatisotopescanbeanadditional,newfingerprintofsoils.ThedomainsofValais(Martigny),theRomandie(Lausanne,Genève,Yverdon)andtheZürichregion(Gockhausen,Hausen-am-Albis, Kindhausen, Oetwil-an-der-Limmat, Wallisellen and Wiesendangen) can be distinguished. A fourth domain(Fribourg),however,slightlyoverlapstheZürichregionandtheRomandiedomainandhenceremainsambiguous.

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Thefactthatothersamplesofcarbonate,quartzandclaymineralsthathavebeenanalysedfromtheMolasseshowsimilarvaluestothesoilsanalysedhere,couldindicatethattheMolasseandthecorrespondingreworkedQuaternarydepositsarethemainsourcesofinorganicsoilmaterial.Eveniftheformationandevolutionofsoilsarestillnotwellunderstoodindetail,biologicalactivity isunlikely to influence themineralogyof soilsanalysedhere inamajorway,although localdifferencesrelatedtoorganicacidsmaybepresent.Thedataprovidenewinsightintochemicalandphysicalprocessesofsoilformationandmaythusbeofhelpforinterpretationsofthegeology,pedology,andforforensics.Moreanalysesofsoilswillcertainlyhelptoprovidefurtherandadditionalconstraintsonsoilprovenanceintimeandspace.

2.19

Elementpartitioningbetweenimmisciblesilicateandcarbonatitemeltsbycentrifugeexperiments

MartinLukasH.J.1,SchmidtMaxW.1,HametnerKathrin2&GüntherDetlef2

1 Institute of Geochemistry and Petrology, ETH, Clausiusstrasse 25, CH-8092 Zürich ([email protected]) 2 Laboratory of Inorganic Chemistry, ETH, Wolfgang-Paulistr. 10, CH-8093 Zürich

Carbonatiteareknownfortheireconomicimportanceastheyareenrichedinrareincompatibleelements,whichareex-ploitedfortechnicalindustry.Themechanismswhichcanformcarbonatitesare:(a)verysmalldegreeofpartialmeltingofaCO2-richmantle,(b)extremedifferentiationofaCO2-richundersilicifiedmagma,(c)bysilicate-carbonatiteliquidim-miscibility.

Thisstudyisfocusedonliquidimmiscibilityanditaimstodeterminetraceelementpartitioncoefficients(KD)betweencarbonatiteandsilicatemeltsinexperiments.TheKDvalueswillthanbeappliedtonaturalconjugatemeltpairsoccurringinvolcanoeseruptingbothsilicateandcarbonatitemagmas.

Thestrategyofthisstudyistoobtainliquidimmiscibilitybyexperiments,segregatethecoexistingliquidsbycentrifuginganddetermineelementpartitioncoefficientsforhighlysodicandhighlypotassiccarbonatite-silicatemeltsystems.Thesepartitioncoefficientsarethenappliedtotestwheatherliquidimmiscibilitywastheprocessformingkamafugite–carbona-titepairs. IncomparisonwiththeonlyexistingpreviouscentrifugestudyfromVeksleretal. (1998),westudyclose-to-natural systemsanddetermine≥40elementpartitioncoefficients.The investigated sodic system is fromLee&Wyllie(1997),thepotassicsystemsimulatestheItalianintra-appeninickamafugite-carbonatitesuite.Kamafugitesarehighlysi-licaundersaturated,haveextremeK2OcontentsandK2O/Na2O>5,crystallizingphologopite,olivine,leucite,melilite,andalsokalsilite.Theyareassociatedwithcarbonatites,whichatsomelocalitiescarrymantlexenolithsindicatingthattheyoriginatefromdepths>45km.

Immisciblecarbonatite-silicatemeltsdevoidofcrystalsareproducedat1GPa,1230°Cand1.7GPa,1220-1250°Cforthesodicandultrapotassicsystems,respectively.Thetraceelementspikedstartingmaterialswerefirstequilibratedinstaticexperiments,reloadedinasinglestagepistoncylindermountedonacentrifugeasdescribedbySchmidtetal.(2006),andrerunatidenticalP-Tconditionsat700gfor3-5hourstophysicallyseparatetheliquids.LA-ICPMSanalyseswereperfor-medonsevencentrifugedexperimentsrepresentingthetwosystems.

Theresultsindicatethatthepartitioncoefficientsareclosetounity.ThealkaliandalkaliearthelementshaveaaffinitytopartitionintothecarbonatitemeltaswellasPandMowhereastheHFSEhaveastrongaffinityforthesilicatemelt.TheLREEelementspartitionweaklyintothecarbonatitemeltwhereastheHREEpreferthesilicatemelt.Theweakparti-tioningoftheLREEintothecarbonatitemeltindicatesthatliquidimmiscibilityisnottheprocessenrichingthecarbona-titesinREE.

REFERENCESLee,W.J.&Wyllie,P. J.1997:Liquid immiscibilitybetweennepheliniteandcarbonatitefrom1.0to2.5GPacompared

withmantlemeltcomposition.ContributionstoMineralogyandPetrology,127,1-16.Schmidt,M.W.,Connolly,J.A.D.,Gunther,D.&Bogaerts,M.2006:Elementpartitioning:Theroleofmeltstructureand

composition.Science,312,1646-1650.Veksler,I.V.,Petibon,C.,Jenner,G.A.,Dorfman,A.M.&Dingwell,D.B.1998:Traceelementpartitioninginimmiscilble

silicate-carbonatite liquid systems:an initial experimental studyusingacentrifugeautoclave. JournalofPetrology,39,2095-2104.

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2.20

InternalflowstructuresincolumnarjointedbasaltfromHrepphólar,Iceland

MattssonHannesB.1,BosshardSonjaA.1,HetényiG1,AlmqvistBjarneS.G.2,HirtAnnM.2,CaricchiLuca3&CaddickMark1

1 Institute of Geochemistry and Petrology, ETH Zürich, Clausiusstrasse 25, 8003 Zurich ([email protected])2 Institute of Geophysics, ETH Zürich3 Department of Earth Sciences, University of Bristol, U.K.

Columnar jointedbasalt fromHrepphólar in southern Icelanddisplay spectacular internal structureswhencut.Thesestructuresfollowtheoverallorientationofthecolumnsanddisplaysemi-circulartocircularfeatureswhencross-cut.Itwaspreviouslybelievedthattheseinternalstructuresformedasaresultofalterationduetocirculationofmeteoricwaterwithinthecolumn-boundingfracturesafteremplacement.However,newfieldobservationsofviscousfingeringwithinthecolumnsandthefactthatapproximately80%ofthesemi-circularfeaturesarefoundwithinthecolumnwhereastheremaining20%arecutbythecolumn-boundingfracturesclearlyshowsthattheseinternalstructuresmusthaveformedpriortocrack-propagation(andarethusprimaryfeatures).

Herewepresenttheresultsoftexturalandpetrologicalanalysesthroughacross-sectionofacolumn,incombinationwithmagneticsusceptibilityandanisotropymeasurementsofthesamesamples.Thevariationintexturesandgeochemistrycanbeattributedtothepresenceofdiffusebandingcausedbyvariationsinthemodalproportionsofthemainphenocrystphases(i.e.,plagioclase,clinopyroxene,olivineandtitanomagnetite/ilmenite).Orientationofplagioclaselathsandtitano-magnetitecrystals (basedonmeasurements in thinsectionsandAMS-measurements)areconsistentwithvertical f lowalignment.Nowhereinthecolumncanevidencefordownwardsf lowbefound(excludingthepossibilityofsmall-scaleconvectioncellsgeneratingthesefeatures).

Itisproposedhere,thatthevolumedecreaseassociatedwithsolidification(typically10-15vol.%forbasalticsystems)andtheincreasingweightoftheoverlyingcrustresultsinupwellingofpartiallycrystallizedmaterialintothecentreofthecolumns.Preliminarynumericalmodelingindicatesthattheisothermswithinindividualcolumnsbecomesteeperwithincreasingdepthinalavaf low(allowingforlargerdisplacementdistances).Weproposethatthisupwellingcanbearathercommonphenomenoninnature,butwithoutthepresenceofchemicallydistinctcompositions(ortexturalbanding)itcanbedifficulttorecognizesuchfeaturesinthefield.

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2.21

MINERALWEATHERINGALONGASOILCHRONOSEQUENCEINAHIGHALPINEPROGLACIALAREA:AMULTIPLEAPPROACH

ChristianMavris1,MarkusEgli1,MichaelPlötze2,JensGötze3,AldoMirabella4,DanieleGiaccai4,WilfredHaeberli1

1 Department of Geography, University of Zurich, Zurich, 8057, Switzerland ([email protected])2 ETH Zurich, Institute for Geotechnical Engineering, Zurich, 8093, Switzerland3 Institute of Mineralogy, TU Bergakademie Freiberg, Freiberg, D-09596, Germany4 Istituto Sperimentale per lo Studio e la Difesa del Suolo, Centro di ricerca per l’Agrobiologia e la Pedologia, Firenze, Italy

Climatechangeandglaciermeltingfeedtheneedforunderstandingtheprocessesrelatedtoweatheringofrecentlyexpo-sedareas.PaststudiesinhighAlpineenvironmentsshowthatclaymineralformationratesarehigherinyoungersoils(<1000yr)thaninoldersoils(>10000yr).However,investigationsofprocessesthatoccurinthefirstdecadesofsoilfor-mationarerare.

InthepresentstudyweinvestigatedthemineralweatheringinarecentlyexposedhighAlpinechronosequence.ThestudywasundertakenintheMorteratschglacierforefield,locatedinSESwitzerland.Theprogressivelyexposedproglacialareaoffersafulltimesequencefrom0to150yroldsurfaces.TherockbasementistheBerninacrystallineunit,mostlycons-titutedofVariscangranitoidrocks(Büchi,1994).Previousmineralogicalstudiescarriedoutinthesoilsoftheproglacialforefield(Mavrisetal.,2010)showadecreaseofbiotiteandepidoteasafunctionoftimeinthefineearthfraction(<2 mm).Mineralogicalmeasurementsoftheclayfraction(<2 µm)werenowcarriedoutusingXRDandDRIFT.Furthermore,ana-lysisinthed(060)rangewerecarriedout.Thedecreasingcontentoftrioctahedralphaseswithtimeintheclayfractionconfirmsactivechemicalweatheringandformationandtransformationofparentrockmineralogy.Measurementoflayerchargesallowedthedetectionofsmectiteandvermiculiteandtheattributionoftheparentphases.Alongtheselectedchronosequence,thesmectitecontentincreasedsteadily.Furthermore,thecombinationofcathodoluminescence(CL)andNomarskiDICmicroscopyfortheobservationofthefineearthfraction(<2mm)allowedtheobservationofcompositionalandweatheringfeaturesinboththeparentmaterialandthesoils.Themineralformationandtransformationprocessesdetectedwithintheconsideredtimespanconfirmthehighreactivityoffreshlyexposedsediments.

Fig.1.Smectitecontentasafunctionofpedogenesis.Squaredot=glacialtill,dot=topsoilsalongtheproglacialarea.

REFERENCESBüchi H. 1994: Der variskischeMagmatismus in der östlichen Bernina (Graubünden, Schweiz). Schweizerische

MineralogischeundPetrographischeMitteilungen,74,359-371Mavris,C.,Egli,M.,Plötze,M.,Blum,J.D.,Mirabella,A.,Giaccai,D.,Haeberli,W.(2010)–Initialstagesofweatheringand

soilformationintheMorteratschproglacialarea(UpperEngadine,Switzerland).Geoderma,155,3-4,359-371.

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2.22

FumarolicaerosolsfromElChichónvolcano,Mexico

MeierMarioFederico1,GrobétyBernard1,2

1 Department of Geosciences, University of Fribourg, Chemin du Musée 6, CH-1700 Fribourg ([email protected], [email protected])2 Fribourg Center for Nanomaterials (FriMat), University of Fribourg, CH-1700 Fribourg

Quiescentvolcanoesareemittingcontinuouslyaerosolparticlesbyfumarolicanddiffusedegassingintothetroposphere.Theimpactoftheseparticlesontheenvironment,e.g.ontheradiationbudget,maybeconsiderably.However,onlyscarceinformationaboutthenatureandtheevolutionofsuchparticlesisavailable(e.g:Matheretal.2003;Pfefferetal.2006).TheaimofthisstudyistocharacterizechemicallyandmorphologicallyfumarolicparticulatematterfromElChichónvolcano(Chiapas,SouthMexico,1150m.a.s.l.).

ForthatpurposeaerosolparticlesweresampledactivelyontopolycarbonateNucleporefiltersandTransmissionElectronMicroscopy(TEM)gridsin2009.Thesamplingdevices,anactivePM10andacorrosionresistantelectrostaticsampler,wereusedatthecraterrim(CR)andclosetothefumarolesinsidethecrater.ThesampleswereanalyzedbyTEMandComputerControlled Scanning ElectronMicroscopy (CCSEM), both combinedwith simultaneous EnergyDispersive Spectroscopyanalysis(EDX).

Severalthousandsofparticlesinthesizefraction0.4–10µmhavebeenanalyzedandclassifiedbyCCSEM.Thesolidparticleconcentrationinsidethecraterwasaround3000particles/liter,whereasontherimtheconcentrationwashalfashigh.Atboth sitesmostof theparticleswerecontaining sulfur.Thedominant fumarolicparticle specieswere sulfur/sulfuricacidparticlesandNa-,K-,Na-K-respectivelyCa-sulfates.Totalsulfurcontainingparticlef luxisestimatedtobe0.1kgs-1.Alkalichloridescouldalsobedetected.Claysareconsideredtohaveanon-fumarolicorigin.Theirabundanceisthesameatbothsamplingsites.Aluminumcontainingparticles (Al-oxides)areclearlymoreabundantattheCR.Thatpointstoahigherinfluenceofsoilparticlesonthetotalparticleconcentrationoutsidethecrater.Manyparticlessampledinside the craterare compositeparticles. Someof themcontainNa-sulfateneedlesandpseudo-hexagonalNa-K-sulfatecrystals.OthercompositeparticlesarecontainingP,S,K,Na,K,(Mg),(Al),(Zn)and(Pb).Thephosphoruspointstoanonmagmaticsource(Obenholzeretal.2003).Mostofthecompositeparticles,includingthePrichparticles,arenolongerpresentattheCR.

ThefumarolesatElChichónemithydrothermalsteamrichinCO2andloweramountsofH2S,acidicspeciessuchasSO2andHClarenearlyabsent(Rouwetetal.2009).Duringthesamplingperiod,thegasemissionswereaccompaniedbygeyseractivitywith increaseddischargeofNa-Cl-SO2waters. Sulfateparticles canbederived fromboth typesof activity.Thepresenceofthedifferentsulfatescanbepartiallyinterpretedasprecipitationproductsresultingfromtheevaporationofgeyserderivedliquiddroplets.Theprecipitationsequenceforsodiumdominatedneutral(Ca)-Na-K-SO4wateris(arcanite)-aphtitalitefollowedbyaNa-sulfatephase,asobserved.Moredataaboutfumarolicaerosolsarecrucialforabetterunder-standingofformationprocessesandtheirimpactontheenvironment.

REFERENCESMather,T.A.,Pyle,D.M.&Oppenheimer,C.,2003:Troposphericvolcanicaerosol.InRobock,A.&Oppenheimer,C.,eds.:

VolcanismandtheEarth’satmosphere.GeophysicalMonograph139,WashingtonD.C.,AGU,189-212.Obenholzer,J.H.,Schroettner,H.,Golob,P.&Delgado,H.,2003:ParticlesfromtheplumeofPopocatépetlvolcano,Mexico

—theFESEM/EDSapproach.InOppenheimer,C.,Pyle,D.M.&Barclay,J.,eds.:Volcanicdegassing.GeologicalSociety,London,SpecialPublications,213,123-148.

Pfeffer,M.A.,Rietmeijer,F.J.M.,Brearley,A.J.&Fischer,T.P.,2006:Electronmicrobeamanalysesofaerosolparticlesfromtheplumeof PoásVolcano,CostaRica and comparisonwith equilibriumplume chemistrymodelling. Journal ofVolcanologyandGeothermalResearch,152,1-2,174-188.

Rouwet,D.,Bellomo,S.,Brusca,L.,Inguaggiato,S.,Jutzeler,M.,Mora,R.,Mazot,A.,Bernard,M.,Cassidy,M.&Taran,Y.,2009:MajorandtraceelementgeochemistryofElChichónvolcano-hydrothermalsystem(Chiapas,Mexico).Geofísicainternational,48(1),55-72.

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2.23

PetrogeneticevolutionofNeogenevolcanisminnorthernUromieh-DokhtarMagmaticBelt:Insightsontheoriginofpost-collisionmagmatism

MonsefReza1,EmamiMohamadHashem2,RashidnejadOmranNematallah3&MonsefIman4

1 Islamic Azad University, Estahban Branch, Iran ([email protected])2 Islamic Azad University, Islamshahr Branch, Iran3 Geology Department Basic Science Faculty, Tarbiyat Modares University, Tehran, Iran4 Shahid Beheshti University, Faculty of Earth Sciences, Tehran, Iran

TheNeogenevolcanicrockswereexposednorthernpartoftheUromieh-DokhtarMagmaticBelt,alongwhichtheNeo-TethyanoceaniclithospherewasclosedduringaperiodbetweenEoceneandOligocene.

Thecollision-relatedvolcanicrocks,whichweremostevidentduringtheEarlyMiocenetoEarlyPliocene,spanthewholecompositionalrangefromandesiticbasalttopargasiticandesiteanddisplaycalc-alkalinecharacter.Theseactivitiesfor-medinrelationtolocalizedextensionalbasinsandweredominatedbypargasiticandesitetoandesiticbasaltlavaf lowsandandesiticbasaltdykes.

MajorandtraceelementsgeochemistrydataexhibitenrichmentinLILEandLREErelativetoHFSE(La(N)/Yb(N)=3-9.7andLa(N)/Nb(N)=2.5-4.5),depletioninNb,TaandTi,andalsohighTh/YbandCe/NbratiosrelativetoMantlearray.TheHFSEdatademonstratethatvolcaniclavashavehighabundancesofNb/YbandNb/Taratios.

Ourgeochemicaldataindicatethatcalc-alkalinevolcanicrockswerederivedfromthemantlemetasomatizedenrichedsourcewitheffectiveofliquidandsedimentf luxcomponentsinheritedfromapre-collisionsubductionslab.

AftercollisionbetweenArabianplateandCentralIranBlockinEarlyCenozoic,thisregionhasexperiencedoflithosphericthinning and volcanismactivity formed in relation to localized extensional regimeduring theEarlyMiocene toEarlyPliocene.Thevolcanismpostdatescontinentalcollision,occurringintranstensionaltectonicenvironment.

Fig1:P-mantlenormalizedREEandtraceelementpatterns

forselectedNeogenepost-collisionvolcanicrocksin

Uromih-DokhtarMagmaticBelt.TheP-mantlenormalizing

valuesarefromSun&McDonough1989.

REFERENCESMcCulloch,M.T.&Gamble,J.A.,1991:Geochemicalandgeodynamicalconstraintsonsubductionzonemagmatism.Earth

andPlanetaryScienceLetters,102,358-375.Sun, S.S. andMcDonough,W.F., 1989:Chemical and isotopic systematics of oceanic basalts: implications formantle

compositionandprocesses.In:Saunders,A.D.andNorry,M.J.(Eds.):MagmatisminOceanBasins.GeologicalSocietySpecialPublicationLondon,313–345.

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2.24

Refiningthegranulite-faciesmetamorphismintheRhodopemetamorphiccomplex–Greece

MoulasEvangelos1,ConnollyJames1,BurgJean-Pierre1&KostopoulosDimitrios2

1 Department of Earth Sciences – ETH-Zurich, Sonneggstrasse 5, CH-8092 Zurich ([email protected])2 Department of Mineralogy and Petrology, Panepistimioupoli Zographou, 15784 Athens, Greece

TheRhodopemetamorphiccomplex(RMC)innorthernGreece-southernBulgariaisastackofsynmetamorphicnappesthrust mostly during Mesozoic times and having experienced extension coeval with magmatic activity during theCenozoic,inparticularduringtheOligocene.Thehigh-pressure(HP)metamorphicrocksofthecentralRhodopeareover-printedbygranuliteandamphibolite-faciesmetamorphism.Thegranulite-faciesmetamorphismhaspreviouslybeenin-terpretedtorecordhigh-pressure,weshowherethatthepressureofgranulitemetamorphismwasunexceptional.

Aretrogressedkyanite-eclogitefromtheintermediatethrustsheetsoftheRMC(outcropnearThermesvillage-northernGreece)wasinvestigatedtoestablishthemetamorphicconditionsduringdecompressionfromeclogite-facies.

Texturesindicatingkyanitereplacementbysymplectitesofcorundum+plagioclase(An40-60)andspinel(Sp50-Hc50)+plagio-clase(An40-60)revealmicro-scalemetasomaticprocesses.Weusedfreeenergyminimizationandcompositionalphasedia-grams(X-Xsections)fortheNa2O-CaO-FeO-MgO-Al2O3-SiO2(NCFMAS)systemtodefinethepressureandtemperature(PT)spaceinwhichthesesymplectiteshaveformed.Thethermodynamicmodellingrevealsthatthegranulite-faciesoverprintoccurredatapressure<ca1.0GPa.ThePTconditionsofthekyanitebreakdownareboundedbytheunivariantphasefields:

garnet=plagioclase+sillimanite+spinelandsapphirine+sillimanite=spinel+cordierite

Our results show thatmodelling of the symplectiticmineralogy in the simplifiedMASH system is inappropriate forNCFMASsymplectites.

2.25

TertiaryPorphyryandEpithermalAssociationoftheSapes-KassiteresDistrict,EasternRhodopes,Greece

MelissaOrtelli1,RobertMoritz1,PanagiotisVoudouris2,MichaelCosca3andJorgeSpangenberg4

1 Départment de Minéralogie, Rue de Maraîchaire 13, CH-1205 Genève ([email protected])2 University of Athens, 15784 Athens, Greece 3 US Geological Survey, Denver Federal Center, Denver 80225, USA4 Institut de Minéralogie et de Géochimie, Anthropole, CH-1015 Lausanne

TheSapes-KassiteresdistrictbelongstotheEasternRhodopesandislocated20kmnorthwestofAlexandroupoli,Thrace,Greece.TertiarymagmatismassociatedwithvarioustypesofmineralizationinnortheasternGreeceandBulgariaisrelatedtopost-orogenicextension(Voudourisetal.2003,Marchevetal.2005).ThisextensionalcontextresultedintheformationofN-orientedfaultsystemscontrollingtheascentofmagmaandtheemplacementoforedeposits.TheSapes-KassiteresdistrictcontainstheSt-Demetrios,ViperandtheSt-Barbaraprospectsandisdescribedasanassociationofporphyryandepithermalgolddepositshostedbyvolcano-sedimentaryrocks(Voudourisetal.2003,Michael2004).Ourstudyarea,to-getherwiththewell-knownPeramaHillproject,ispartofazoneintheEasternRhodopesstraddlingGreeceandBulgaria,whichisthefocusofcontinuousexplorationinterestforgoldbyminingcompaniesoverthelastdecade.

TheearliestmineralizingeventistheKonosMo(-Cu)porphyryhostedbyagranodiorite-tonaliteandcontainingmainlydisseminatedpyriteandsomeCu-mineralizationinsericiticalteredhostrocks,whichiscrosscutbymolybdenite-pyrite

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veins,dark-greybandedquartzveins(B-veins)andsulfide-richgypsumveins.Epithermaleventsformthepredominantmineralizationofthedistrict,startingwithhigh-sulfidationmineralizationatSt-Demetrioswithhydrothermalvuggysi-licabrecciaandnativegoldassociatedwithtellurides,sulfidesandsulfosalts,followedbytwodifferentlow/intermediate-sulfidationeventscharacterizedbyamethyst-chalcedonyveinsrelatedtoquartzadulariaalterationandmilkyquartzbasemetalveinsrelatedtosericiticalteration.

Fluidinclusionmicrothermometricdatawerecollectedfromquartz,calcite,sphaleriteofthemineralizedveinsfromtheSapes-Kassiteresdistrict,andshowanevolutionofhomogenizationtemperatures(withoutpressurecorrection)rangingfrom560°C, corresponding to thehigh-temperature porphyry system, to 160°C, related to a superficial or epithermalenvironment.Anearlyboilingassemblagearound500 °C iscrosscutbybrine inclusiontrailsyieldinghomogenizationtemperaturesaround240°Cwithsalinitiesbetween30and50wt.%NaClequiv.Fluidinclusionsrelatedtotheepithermalveins(Viperamethyst-chalcedonyveins,andmilkyquartz-calciteveins)yieldhomogenizationtemperaturesbetween170to315°Candsalinitiesbelow6wt.%NaClequiv.

Oxygen isotope values combinedwith f luid inclusiondata reveal thepresenceof amagmatic source formineralizingf luidsrelatedtotheporphyrysystemandtheepithermalveins,withmeteoricwatercontributingtotheoxygenisotopiccompositionoftheepithermalveins.

Accordingtothe40Ar/39Ardata,theSapes-Kassiteresdistrictincludesmagmaticandmineralizingevents,whichtookplacebetween31.3and33.1Ma.ThisstudyrevealsthattheSapes-Kassiteresmagmatismandmineralizationwerecontempo-raneousatabout32MawithotherEasternRhodopesoredistrictsinBulgaria,likeMadjarovoandZvezdel.Atthedistrictscale,the40Ar/39Aragestendtoconfirmthechronologyofthemagmatismandmineralizationeventsobservedinthefield(Figure1).Theporphyrymineralization(biotitecoolingage:32.6±0.5Ma)precedesthebiotiteageofthepotassicaltera-tionat32.0±0.5Ma.Adulariafromthelow/intermediatesulfidationsystemyieldedanageof31.5±0.2Ma.Onesetofthemagmaticsteamaluniteshasaplateauagesof31.9±0.2Maoverlappingwiththebiotiteandadulariaages.Anothermagmaticsteamaluniteyieldsaslightlyyoungerageof31.2±0.4Ma.

Figure1.ModifiedgeneticmodelbyVoudouris(1993).Thecoloreditemshighlightthenewcontributionsofthisstudy.

REFERENCESMarchev, P., Kaiser-Rohrmeier,M.,Heinrich,C.,Ovtcharova,M., vonQuadt,A., Raicheva,R., 2005,Hydrothermal ore

deposits related to post-orogenic extensionalmagmatism and core complex formation: The RhodopeMassif ofBulgariaandGreece:OreGeologyReviews27,p.53-89.

Michael, C., 2004, Epithermal systems and goldmineralization inwestern Thrace (NorthGreece) : Bulletin of theGeologicalSocietyofGreecevol.XXXVI,p.416-423

Voudouris,P.,1993,Mineralogische,mikrothermometrischeundgeochemischeUntersuchungenanepithermalenAu-AgGangmineralisationenbeiKassiteres/Sape(Nordostgriechenland).PhDThesisatHambourgUniversity.

Voudouris,P.,Melfos,V.,Vavelidis,M.,Arikas,K.,2003,GeneticrelationbetweentheTertiaryporphyryCu(-Mo)andtheepithermalAu(-Ag)depositsintheRhodopesmetallogenicprovince,Thraceregion,NorthernGreece:Eliopoulosetal.(eds)MineralExplorationandSustainableDevelopment,SGAmeetingAthensAugust2003,p.542-544.

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2.26

Reactivemultiphaseflowatthepore-scale:themeltingofacrystallineframeworkduringtheinjectionofbuoyanthotvolatiles.

ParmigianiAndrea1,HuberChristian2,BachmannOlivier3&ChopardBastien1

1 Computer Science Department, University of Geneva, CH-1211 Geneva 4, Switzerla(anderea.parmigiani @unige.ch)2 School of Earth and Atmospheric Sciences, Georgia Institute of Technology, GA 30332, USA.3 Department of Earth and Space Sciences, University of Washington, WA, USA.

Multiphasereactivef lowsoccurnaturallyinvariousenvironmentsintheshallowsubsurface,e.g.CO2injectionsinsatu-ratedreservoirs,exsolvedmethanef luxinshallowsedimentsandH20-CO2volatilesinmagmaticsystems.Becauseoftheirmultiphasenaturetogetherwiththenonlinearfeedbacksbetweenreactions(dissolution/meltingorprecipitation)andthef lowfieldatthepore-scale,thestudyofthesedynamicalprocessesremainsagreatchallenge.Inthisstudywefocusontheinjectionofbuoyanthotvolatilesexsolvedfromamagmaticintrusionunderplatingacrystal-rich magma (porous medium). We use some simple theoretical models and a pore-scale multiphase reactive latticeBoltzmannmodeltoinvestigatehowtheheatcarriedbythevolatilephaseaffectstheevolutionoftheporousmediumspatiallyandtemporally.Wefindthatwhenthereactionrateisrelativelyslowandwhentheinjectionrateofvolatilesislarge(highinjectionCapillarynumber),thedissolutionoftheporousmediumcanbedescribedbyalocalPecletnumber(ratioofadvectivetodiffusivef luxofheat/reactantinthemaingaschannel).Whentheinjectionrateofvolatileisreduced,orwhenthereactionrateislarge,thedynamicstransitiontomorecomplexregimes,wheresubverticalgaschannelsarenolongerstableandcanbreakintodisconnectedgasslugs.

Forthecaseoftheinjectionofhotvolatilesincrystal-richmagmaticsystems,wefindthattheexcessenthalpyadvectedbybuoyantvolatilespenetrates theporousmediumoverdistances~rPe,where r is theaverage radiusof thevolatilechannel(~poresize).Thetransportofheatbybuoyantgasesthroughacrystalmushisthereforeinmostcaseslimitedtodistances<meters.Ourresultsalsosuggestthatbuoyantvolatilescancarrychemicalspecies(Li,F,Cl)farintoamushastheir corresponding localPecletnumber is severalordersofmagnitudegreater than that forheat,owing to their lowdiffusioncoefficients.

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2.27

Constrainingcalciumisotopefractionationincorals

PretetChloé1,FelisThomas2&SamankassouElias1

1 Département de géologie et paléontologie, rue des maraîchers 13, CH-1205 Genève, Switzerland ([email protected])2 MARUM-Center for Marine Environmental Sciences, University of Bremen, 28359 Bremen, Germany

Basedonamulti-proxydatasetconsistingofd44Ca,d18OandSr/Ca,thispreliminaryreportdiscussestheparametersthatcontrolthecalciumisotopefractionationintropicalcorals.Potentialfactorsthatcontrolthecalciumisotoperatioincoralskeletonincludebiologicalfactors(vitaleffects),tempera-tureandsalinity.Currentlythecalciumpathwayandisotopicfractionationincoralsisnotfullyconstrained.Therefore,detailedmeasurementsandamulti-proxyapproachappearfundamentalfortheunderstandingofparametersthatinflu-encethefractionation.

OurdatasetisbasedonfossillastdeglacialcoralsamplesfromTahiti,coredduringtheIODPExpedition310(Camoinetal.,2007).Foranaccuraterecord,thecoralskeletonwasmicro-drilledatsubseasonalresolution.CaandOisotopiccom-positionaswellastheSr/Caratioweremeasured,usingthesamesample.ForCa,weusedaTIMSFinniganTritonT1,followingthemethoddescribedinHeuseretal.(2002).

Ourpreliminaryresultsshowthatthefractionationisalmostconstantwithinerrorbars.Norelationshipbetweenpreci-pitationrateandcorald44Caisrecognized.

Subseasonaltemperaturesvariationsreconstructedfromcorald18OsignalandSr/Caratioarenotmirroredincorald44Ca.TheweaktemperaturedependencereportedbyBöhmetal.(2006)ispossiblynottheonlyparameterthatisresponsibleforthefractionation.

Removingsea-surfacetemperaturecomponentfromthecorald18Osignal(d18Oseawater)resultsinacorald44Carecordthat

revealssomesimilaritytothereconstructedd18Oseawaterrecord,pointingtosalinityasapotentialfactorthataffectscorald44Ca.However,wenotethatinmoderncoralstheseasonalcycleofsalinityatTahiticannotberesolved(Cahyarinietal.,2008).Thesepreliminaryresultsrequirefurtherinvestigation,includingmeasurementsofskeletonoriginatingfromcoralsculturedunderwell-monitoredenvironmentalconditions.

Furthermore,weplantomeasuretheisotopiccompositionofdifferentmicrostructuralpartsofcorals(e.g.,calcificationcenterversusfibers)inordertobetterconstrainthecalciumisotopefractionationprocesses.

REFERENCESBöhm,F.,Gussone,N.,Eisenhauer,A.,Dullo,W.,Reynaud,S.,&Paytan,A.2006:Calciumisotopefractionationinmodern

scleractiniancorals.GeochimicaetCosmochimicaActa,70(17),4452-4462.CahyariniS.Y.,PfeifferM.,TimmO.,DulloW.,&SchönbergD.G.2008:Reconstructingseawaterd18Ofrompairedcoral

d18OandSr/Caratios:Methods,erroranalysisandproblems,withexamplesfromTahiti(FrenchPolynesia)andTimor(Indonesia).GeochimicaetCosmochimicaActa,72,2841-2853.

Camoin,G.F., Iryu,Y.,McInroy,D.&theIODPExpedition310Scientists2007:ProceedingsoftheIODP310. IntegratedOceanDrillingProgramManagementInternational,Inc,Washington,DC.

Heuser,A.,Eisenhauer,A.,Gussone,N.,Bock,B.,Hansen,B.T.,Nägler,T.F.2002:Measurementofcalciumisotopes(d44Ca)usingamulticollectorTIMStechnique.InternationalJournalofMassSpectrometry,220,385–397.

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2.28

ComplexdynamicsintheSesiaZonesubductionsystemdeducedfrommultiplegenerationsofwhitemicaandallanite:thepowerofmicrotex-turalanalysiscombinedwithpetrochronology

DanieleRegis1,MartinEngi1,DanielaRubatto2,JamesDarling1

1 Institut für Geologie, Universität Bern, Baltzerstrasse 3, CH-3012 Bern ([email protected])2 Research School of Earth Sciences, Australian National University, Canberra

Researchworldwideontheevolutionofterrainswithhigh-pressure(HP)rocksaimstoelucidatethegeodynamicallyfun-damentalprocessesatconvergentmargins.TheWesternAlps,notablytheirinternalparts(Sesia-LanzoZone,DentBlanchenappe,andsmallerklippenunits),havelongbeenrecognizedasaclassicHPterrane:asubstantialareaofpredominantlycontinental,polycyclicbasementtransformedtoblueschistoreclogitefaciesintheAlpineorogeny.However,recentregi-onalwork(Babistetal.,2006)hasindicatedsubstantialgapsandinconsistenciesintheclassicviewoftheWesternAlps,andnewmodelsemphasizingthesequenceofregionalpoly-deformationandpoly-metamorphismhavebeenproposed.Toretracethestepsofthiscomplexevolution,itisessentialtolinkthedetailedpetrographyandmicrochemicalanalysisofthemajorandaccessoryphaseswiththeirmicrotexturalrelationsandsubgrain-scalegeochronology,usingaretentiveisotopicsystem.

Wepresentacasestudyonasinglepoly-deformedeclogitefaciessamplefromtheSesiaZone(ItalianWesternAlps),whichcontainsphengiteandallanitecrystalswithmultiplemetamorphicdomains.

Thesample,collectedintheScalarovalley,consistsofquartz(60%),phengite(20%),allanite/epidote(10%),detritalfeldspar(2%)andalbite (5%)withaccessorymonazite,apatite, titaniteandzircon.Twofoliationsaremarkedbywhitemicaofdifferentcomposition:Phengite(Wm2-Phe2)markingthemainfoliation(S3)containslargerelicf lakes(Wm1-Phe1,pre-S3).Texturallyoldphengitecores(Phe1)arerimmedbymuscovite(Wm1),thecompositionofwhichisidenticaltothatofwhitemicacoresinS3(Wm2).Thelatterareinturnsurroundedbyphengiterims(Phe2).Occasionally,Phe1formsreliccoresinthemicaalignedalongS3.

InthesamequartziteREE-richallanitecoreshaveafirstrimofREE-poorallaniteandanexternalrimofepidote.Corrodedrelicsofmonaziteareoccasionallypresentintheallanitecore.Theallanitecontentsdecreasefromcore(Alncore:REE+Y0.5-0.44a.p.f.u.)torim(Alnrim:REE+Y0.3-0.24a.p.f.u)totheepidoterim(Ep:REE+Y<0.05a.p.f.u.).Bothtypesofallani-teareCe-dominated,incorporatingonlysmallamountsofLaandNd.ThezoningseeninBSEimagesisduetodifferencesinREE,ThandUcontents,whichgenerallydecreasefromcoretorim.TheepidoterimisFe-andSr-rich.

Allanitecoresandrimscontainminutephengiteinclusions.ThesewereanalyzedbyEMPtocomparetheircompositionwiththatofmicamarkingtheS3foliation.Abundantmicainclusionsintheallanitecoresareidenticalincompositiontothetexturallyoldestphengitepreservedinthesample(Phe1).Allaniterimscontaininclusionsofmicas,thecompositionofwhichareindistinguishablefromthoseofthelowpressuremicas(Wm1/Wm2).

ThetwogenerationsofallaniteweredatedbyionmicroprobeusingtheTh-Pbsystem.TheepidoterimwastoorichincommonPbtoobtainreliableagedata.TheREE-richallanitecoresyieldconsistent208Pb/232Thageswithweightedmeanof75.6±0.8Ma(10analyses,MSWD1.02).TheREE-poorallanitemantleissystematicallyyoungerat69.8±0.8Ma(11analyses,MSWD1.8).Thetwoallanitepopulationsarethusindicativeoftwometamorphicstagesthatpre-datethe~65MaHPas-semblagethathasgenerallybeenacceptedastheageoftheeclogitefaciesmetamorphismintheSesiaZone(Ingeretal.1996,Duchêneetal.1997,Rubattoetal.1999).ThelatterislikelyrepresentedbythetexturallylateHPfoliation(Phe2)preserved inthesample.ThismayexplaintheremarkablediversityofAr-AragedatareportedbyVenturini (1995) forsamplesfrommanylocalitiesintheSesiaZone,includingtheCimaBonzearea,wherethepresentsamplewastaken.

Thisstudyrevealsthatthesubduction-collisionhistoryhasproducedacomplexrecordinsinglerocksamples,inthiscaseanimpurequartzite.Combiningmicrotexturalanalysisandpetrochronology,specifiedstagesofthemetamorphicevolu-tionandpolyphasedeformationwerediscerned;SHRIMPdatingofselectgrowthdomainsofallaniteyieldeda(minimum)durationof~6MafortheagedifferencebetweentwostagesoftheHP-evolution.Itisnotclearwhytheeclogitestageat65Masimplyleftnoimprintinthistypeofsample,whereasearlierstagesdid.Accordingtotheregionaltectonicframe-work(Babistetal.2006),thetwomainbasementblocksoftheSesiaZone(i.e.theBardandMombaroneunits)wereamal-gamatedwiththetrailofBonzemetasedimentsbetweenthematHP-conditions,priortothecomplexexhumationhistory.

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REFERENCESBabistJ.,HandyM.R.,HammerschmidtK.&Konrad-Schmolke,M.,2006.Multi-stageexhumationofhighpressurerocks

fromasliverofcontinentalcrust:anexamplefromtheSesiazone,ItalianWesternAlps.Tectonics,26:25.DuchêneS.,Blichert-ToftJ.,LuaisB.,TéloukP.,LardeauxJ.-M.,AlbarèdeF.1997.TheLu-Hfdatingofgarnetsandtheages

oftheAlpinehigh-pressuremetamorphism.Nature387,586.IngerS.,RamsbothamW.,CliffR.A.,&RexD.C.,1996.MetamorphicevolutionoftheSesia-LanzoZone,WesternAlps:

timeconstraintsfrommulti-systemgeochronology.Contrib.Mineral.Petrol.126,152.RubattoD.,GebauerD.&CompagnoniR.,1999.Datingofeclogite-facieszircons:theageofAlpinemetamorphisminthe

Sesia-LanzoZone(WesternAlps).EarthPlanet.Sci.Lett.167,141.Venturini,G., 1995.Geology, geochemistry and geochronology of the inner central Sesia Zone (WesternAlps, Italy).

MémoiresdeGéologie(Lausanne),25:148p.

2.29

ThousandYearsofmassiveIronProductionintheDogonCountry(Mali,WesternAfrica):Technology–Economy-Environment

SerneelsVincent1

1 Department of Geosciences, University of Fribourg, Chemin du Musée 6, CH-1700 Fribourg ([email protected])

Inpre-industrialsocieties,irontoolsareessentialforagricultureandironweaponsforwarfareandpoliticalpower.IronproductiontookplaceeverywhereinAfrica,longtimeago(atleast2’500years)andwelbeforethecolonisation.Thepro-ductiontechniqueisalwaysbasedonthe“bloomeryprocess”:solidstatereductionofironoxidesintometalbyreactionwiththecarbonmonoxidefromthecombustionofcharcoal.AlloverAfrica,societiesdevelopedanincrediblyhighnum-berofdifferentproductionlinestoobtainironfromahugherangeoforesusingverydifferentfurnaces(verysmalltovery large,windorbellowsdriven, free standingor sunked,etc).Thereason for this technologicalvariability remainsunexplained.

Fortenyears,theancientironproductioninthedogonCountry(centralMali,WestAfrica)isinvestigatedonthefieldandinthelaboratory.Theaimofthestudyistheunderstandingofthetechnologiesandthemeasureoftheimpactofthisproductiononthesocietiesandtheenvironment.

Inthestudiedarea(15’000km2),about150productionsiteshavebeenlocated.Sevendifferenttechnologicaltraditionshavebeencharacterisedindifferentareas.Averyremarkableconcentrationofremainshasbeenidentifiedinarestrictedarea(500km2),aroundthevillageofFiko.

Thesystematicsurveyoftheproductionsitesrevealedabout15largecomplexes,characterisedbyhugheheapsofslagandfurnaceremains.Theslagheapsaremappedindetailduringfieldworkandthevolumesofwastearecalculated.Furnaceremainsareexcavatedandstratigraphictrenchesarecuttedintotheheaps.Slags,ores,liningsandcharcoalaresystema-ticallysampledforlaboratorystudies(XRF,XRD,SEM-EDS).Datesareobtainedby14Concharcoal.

Thetechnologyisalwaysthesame,basedonverylargefurnace(3-4m3)usingcharcoalandnaturaldraftandnobellows(lowtemperatures1100°c/longtimes>24h).Lateriticores,minedinseveralpointsalloverthearea,areused.Gradesarelowinthenaturalore(Fe2O355–65%)butenrichmentbyhandsortingallowstoincreaseitsignificantly.Tappedslagscontainingfayaliteandfewfreewüstitearethetypicalwastes(FeO45–50%).

Thesizesoftheheapsrangefrom5’000to40’000tons.ThetotalamountofslagfromthetechnologicaltraditionofFikocanbeevaluatedto300’000tons.Thequantityof ironcanbeestimatedonthebasisofachemicalbalancecalculatedbetweentheoreandslag.Thetotalquantityofironmusthavebeenover100’000tons.

Theproductionstartedprobablyaround500ADbutdevelopedmainlybetween1000and1750ADatthetimeoftheriseoftheMaliEmpire.Theproductionriseduptoaquasiindustriallevel(100tons/year),involvingalargepartofthelocalpopulationandwithasignificantimpactonthewoodressources(2000tonswood/year).

This study is part of the global interdisciplinary project “Human Population and Paleoclimatic Evolution in West Africa” leaded by prof. E. Huysecom (Geneva) and funded by the SNF, the SLSA and several additional sources. The various aspects of the archaeometallurgical studies involved several european and african researchers: V. Serneels, S. Perret, M. Mauvilly, I. Katona, R. Soulignac (Fribourg), C. Brunner (Geneva – Toulouse), B. Eichhorn (Frankfurt), B. Traoré (Bamako – Paris), A. Dembélé (Bandiagara).

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2.30

TheAdamellobatholith(Italy):afossilmagmachamberoraccumulationofmagmapulses?

SkopelitisAlexandra1,SchalteggerUrs1,UlianovAlexey2&BrackPeter3

1 Département de Minéralogie, Rue de Maraîchers 13, CH-1211 Genève 4 ([email protected], [email protected])2 Institut de minéralogie et géochimie, Anthropole, CH-1015 Lausanne ([email protected])3 Departement Erdwissenschaften, ETH Zürich, CH-8092 Zürich ([email protected])

Wewanttostudyplutonsandbatholithsindetailtoelucidatetheirmodesofformation,andinparticular,toreconstructthetimerequiredfortheiremplacement.Thislatterinformationislinkedtotheoverallthermalbudgetoftheintrudedareaandthecoolingrateoftheintrudedmagmaticbodies.Itisimportanttoknowhowthetimescalesofsolidificationrelatetothetimeelapsingbetweentheemplacementoftwoconsecutivemagmabatches.Inotherwords,wewanttoknowtowhatextentwhichpartsofaplutonwerepresentina,atleastpartially,moltenstate.

ThisstudyfocusesonthetimeneededtobuildtheAdamellobatholithintheItalianAlps,mainlyinthenorthernpart,whichcomprisestheRédiCastello(RdC),theAdamello,theAvioandthePresanellasuperunits(Fig.1).Previousagedeter-minationsfromtheAdamellorocksshowayoungingtowardsthenorth,basedonU-PbzircondataandK-ArandRb-Srresults(summariesinCallegari&Brack,2002;Schalteggeretal.,2009).Thesouthofthebatholithischaracterizedbymoremaficcompositionsrangingfromgabbroictotonalitic,whereasthenorthiscomposedprincipallyoftonalite,leucotona-liteandtrondhjemiterocks(Brack,1983).Moreover,previousisotopestudiesacrosstheAdamelloshowedanincreaseofthe87Sr/86Srand18O/16Oratiosfromsouthtonorth,indicatinganincreasingcrustalcontaminationtowardsthenorth(DelMoroetal.,1983;Dupuyetal.,1982),confirmedbypetrographicalchangesinthetonalites,suchasincreasingabundanceofbiotitecomparedtoamphiboleinthesamedirection.Inthisproject,geochronologyandwholerockaswellasmineralchemistrywillbeusedtounderstandtheformationofthetonalites.Weattemptunderstandinganddistinctionofinheri-tedgeochemicalcharacteristicsfromthesourceandthoseacquiredduringfractionationandcrystallisation.

RocksfromthecenterandthenorthoftheAdamelloshowarestrictedrangeincomposition(diorite-granodiorite,63-70%wtSiO2)althoughtherockshavedifferentmineralogy,grainsizeandtexture.Indeed,thetexturesobservedinrocksfromthenorth-easternborderareasarespecificbecauseoftheirfoliation,probablyduetodeformationinconnectionwiththeadjacentTonaleLine.ThepreliminarygeochemicaldatahighlightthattheRdChasametaluminouscomposition,where-astheothersunits-youngerandsituatednorthwards-aremoreperaluminous.Laserablation-ICP-MSU-Pbagedetermi-nationsonzirconfromtonalitesoriginatingfromthecentralandnorthernpartsofthebatholithhavebeencarriedouttodeterminetheageofcrystallizationandreconstructtheintrusionsequence.FirstresultsconfirmthatthecenterandnorthernpartoftheAdamelloemplacedbetween43and34Ma(Fig.1).Withourpresentanalyticalprecisionof0.4-1%(N=8-32)of the 206Pb/238Uagewecandemonstrateourability toresolvesuchagedifferencesandhavearguments that theAdamellobatholithformedincrementallybyseveralpulsesyoungingtowardsthenorthandshowingdifferentcomposi-tion.TheCLimagingperformedbeforeLA-ICP-MSanalysisrevealedwellcrystallizedmagmaticzonationsandxenocrysticcoresinparticularfornorthernunits.Finally,theseresultsclearlyfavouranamalgamationofdistinctmagmaticpulsesovermillionsofyearsthatpreviouslydifferentiatedinadeepermagmaticsystemastheprocessformingtheAdamellobatholith.

We acknowledge funding of FNS in the frame of ProDoc project Adamello 4-D.

REFERENCESBrack, P. 1983:Multiple intrusions examples from the Adamello batholith (Italy) and their significance on the

mechanismsofintrusions.Mem.Soc.Geol.It.26,145-157Callegari,E.&Brack,P.2002:GeologicalmapoftheTertiaryAdamellobatholith(NorthernItaly)explanatorynotesand

legend.Mem.Sci.Geol.54,19-49DelMoro,A., Ferrara,G., Tonarini, S.&Callegari, E. 1983: Rb-Sr systematics on rocks from theAdamelloBatholith

(SouthernAlps).Mem.Soc.Geol.It.26,261-284Dupuy,C.,Dostal,J.&Fratta,M.1982:GeochemistryoftheAdamelloMassif(NorthernItaly).Contrib.Min.Pet.80,41-48Schaltegger,U.,Brack,P.,Ovtcharova,M.,Peytcheva,I.,Schoene,B.,Stracke,A.&Bargossi,G.2009:Zirconandtitanite

recording1.5millionyearsofmagmaaccretion,crystallizationand initialcooling inacompositepluton (southernAdamellobatholith,northernItaly).EarthPlanet.Sci.Lett.186,108-218

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Figure1.GeologicalmapoftheAdamellobatholith,indicatingournewLA-ICP-MSU-Pbagesonzircon(ModifiedafterBracketal.,un-

published)

2.31

MineralogicaltechniquesandethnoarchaeologyappliedtothestudyofsmithingslagsinMali(Africa)

SoulignacRaphaëlle1

1 Department of Geosciences, Chemin du Musée 6, CH – 1700 Fribourg ([email protected])

Archaeologicalexcavationsoftenrevealhemisphericalpiecesofslagthatarethewasteresultingofthesmithingofironinahearth.Theyareformedbytheaccumulationofseveralfusedmaterialsatthebaseofthehearth,betweenthelight-ingandtheextinctionofthefire.Smithingslagsshowahighvariability(size,weight,shape,internalstructure,materialstheyaremadeof)ref lectingthecomplexityofthesmithingwork:variabilityofstartingmaterials,thermomecanictreat-ments,skillsofthesmith,economicpressure.

Withthisintentiontounderstandinmoredetailsthoseslags,weundertookanethnoarchaeologicalapproachwithtra-ditionalsmithsoftheDogongroupinMali.Thisethnoarchaeologicalapproachisbasedontheobservationandtherecordoftheproductionof126traditionalhoesofironor“daba”in4villagesof2ethnicalgroupswithseveralsmiths.Theyweregiveneachtimevariousstartingmaterialswithdifferentcomposition(%C:0.17,0.35,0.45)orshape(barsof4x4cm,2x2cm,1x1cmetc).Thewastes(slagsandhammerscales)havebeencollectedafteronesingleforgingorafteroneworkingday.Theyareunderstudyinthelab,usingmineralogicaltechniques:XRF,XRD,SEM-EDXS.Thefirstresultswillbediscussed.

Itappearsthatforonesinglepieceofiron,thequantityofironlostduringtheoperationvariesfrom7to25%.Ifthesmithhastoweldtogether2piecesofiron,thenthelengthoftheoperationincreasesandalsotheamountofironlost,upto60%.

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2.32

MiningarchaeologicalstudiesinEasternPyrenees,France:Baillestavyironminingarea

CălinG.Tămaş1,2,GabrielMunteanu3,BéatriceCauuet3&GérardMut3

1 Department of Geosciences, University of Fribourg, 6, chemin du Musée, CH-1700 Fribourg ([email protected])2 Faculty of Biology and Geology, University Babeş-Bolyai, 1, M. Kogălniceanu str., 400084, Cluj-Napoca, Romania3 Laboratoire des Travaux et Recherches Archéologiques sur les Cultures, les Espaces et les Sociétés (TRACES), Université Toulouse 2 Le Mirail, CNRS UMR 5608, Maison de la Recherche, 5 allées Antonio-Machado, 31 058 Toulouse Cedex 09, France

SeveralirondepositshostedinLowerCambrianlimestonesanddolomites(CanaveillesFormation)areknowninthenort-hernpartofCanigouMassif,EasternPyrenees,France(Guitardetal.,1998).Accordingtotheabovementionauthorsse-veraldepositslikeBatère,Escaro-Escoums,Aytua-Torrent,Casteil-Falguerosa,Sahorre,Fillols-Taurinya,leLlech,laCoumehavebeenmineduntilmid20thcenturywhentheminingactivityfinallystopped.

BaillestavyisasmallvillagesituatedclosetolaCoumedeposit.Thislocalityrepresentsaminingsitebutinthesametimeitisknownduetothelargeamountofironslags.Archaeologicaldiggingscarriedoutwithintheslagdepositofthechur-chSt.AndrewfromBaillestavy(Mut,2001)pointedoutametallurgicactivitybacktoGaulandRomantimes(2ndcenturyBC–1stcenturyAD).InsteadofthepresenceofAncientslagwastedumpsinBaillestavy,accordingtoFinot(1902)theironexploitationstartedonlyin1830.

MiningarchaeologicalstudiesstartedrecentlyinBaillestavyareahavingseveralaims:

-tomakeanuptodatereviewoftheaccessibleminingvestigesandtheirconservationstate;-toidentifydifferentperiodsofminingbasedonpeculiaritiesofdiggingtechniques;-datingoftheoldestminingactivity.

Thestudydevelopedduringthreefieldworkcampaignsbeingfocusedonsurfaceandundergroundexploration,identifi-cationofallaccessibleminingworks,topographyoftheworks,archaeologicalobservations,geologicalmapping,andar-chaeologicaldiggings.FourminingsiteshavebeeninvestigatedinthevicinityofBaillestavy:MasMorer,PeñaBlanca,laCoumeandMasBourasse.

Takingintoaccountthediggingtechnique,atleastthreeperiodsofactivityhavebeenobserved:

1–handtoolswithnarrowtraces;2–Catalantypechisel;3–blastholes(twotypes).

Theorebodiesandtheirhostrockshavebeenmappedforalltheidentifiedminingsites.Thegeologicalstudyoftheun-dergroundworksgavemoreinformationsconcerningthegenesisoftheorebodiesandhelpedtobetterunderstandthedevelopmentofthemines.

ThearchaeologicaldiggingsconductedintheundergroundworksfromMasBourasseminingsector,situatednorth-westoflaCoumedeposit,allowedMunteanu(2010)tocertifythattheironoreswereminedduring1stcenturyAD.

REFERENCESGuitard,G.,Laumonier,B.,Autran,A.,Bandet,Y.&Berger,G.M.1998:CartegéologiquesdelaFranceà1/50.000.Notice

explicativedelafeuillePrades,198p.Finot,M.1902:Procès-verbaldevisitedesrecherchesdeminesdeferde laSociétédePauillacàBaillestavyetEstoher.

MinistèredesTravauxPubliques,ServicedesMines,Dépt.desPyrénéesOrientales,Prades,no.1246,8p.Munteanu,G.2010:LedistrictminierdeBaillestavy(PyrénéesOrientales).Laproductionduferdel’Antiquitéàl’époque

moderne–exploration,topographie,chronologieetgéologiedesminessouterraines.MasterII,UniversitéToulouseleMirail(unpubl.).

Mut,G.2001:LesforgesdeBaillestavy,inSablayrolles,R.(ed.),LesressourcesnaturellesdesPyrénées.Leurexploitationdurantl’Antiquité,Entretiensd’archéologieetd’histoire,St-Bertrand-de-Comminges,2001,p.141-153.

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2.33

FossiliferouspotteryinAjoie(NWSwitzerland)andadjacentregionsfromLaTèneandGallo-romansites:Informationonproductionanddis-tributionthroughmicroscopicandchemicalanalyses

Thierrin-MichaelGisela

Department of Geosciences, University of Fribourg, ch. du musée 6, 1700 Fribourg et Section archéologie et paléontologie, Office de la cul-ture du Canton du Jura, 2900 Porrentruy

Fossiliferous,alsocalled“shell-tempered”,potteryispresentedasaphenomenoninlateLaTèneandGallo-romanperiodsinseveralregions–likeNormandy,BelgiumandSouthEngland.Inmostcasestheseceramicproductionsarelinkedtoclayoutcropsinthesameregion.Insomeinstances,however,thesewaresarethoughttohavebeenwidelydistributedfromoneproductionarea.

FossiliferouspotteryisthemostimportantfabricgroupatmidtolateLaTènesitesinAjoieandremainssignificantamongGallo-romanmaterial(7sitesconsidered).Hand-formedbowlsofdifferentdimensionarethemostfrequentform.Thesefindingsallowedadiachronicstudyofthispottery,spanningover300yearsansweringfollowingquestions:whichrawmaterialswereused?,thesameclay(s)throughout?,sameordifferingpreparationintime?

ThepresenceoffossiliferouspotteryisalsowelldocumentedoncontemporarysitesinthenearbyBaselregion,amongthemthekiln-siteofSissach-Brühl(Basel-Landschaft,Switzerland).WhileverycoarsepiecesfromAjoiearedistinctiveandseemtooccuronlythere,afinerfabricispresentonallsites.Macroscopically,thematerialfromdifferentsitesisundis-tinguishable.Werethereonlyfewproductionsitesandexchange,ormanyproductions?Inordertodeterminethis,piecesfromSissach-BrühlandthreeLaTènesettlements(mostlyhand-formedbowls),aswellassherdsofhand-formedcookingpotsfromtheRomantownAugustaRauricorum(Basel-Landschaft,Switzerland)andsurroundingvillae,werecomparedtothefindsfromAjoie.

Macroscopic,microscopicandchemical(XRF-WDS)comparisontovirgulamarlfromtheupperJurassic(Kimmeridgian)provedthisparticularclaytobeusedinAjoie–eitherpureorcrushedandmixedwithnon-calcareousquarternaryclays.Outcropsofthemarlylayerareeasilyaccessiblefromallthesites.Somegallo-romanpiecesrevealedanotherpreparation:crushedspathiclimestone,locallyavailable,mixedwithnon-calcarousclay.

ThesherdsfromtheBaselregionallshowfossilassemblagesdifferentfromtheAjoiepottery.FossiliferousmarlylayersfromtheDoggercertainlyprovidedtherawmaterialsforsomeofthem,whileothersappeartobemixtures(naturalorintentional)ofdifferentnotyet identifiedclays (the identification isdifficultalso,becausethinsectionsfromceramicsherdsdonotalwaysshowdiagnosticfossilfragmentsandassemblages).Thisdiversityinrawmaterialsupportstheas-sumptionthatthiswarerarelytravelledfarfromtheproductionsiteinthediscussedregionofNWSwitzerland.DuringtheLaTèneperiodatleast,thereisnoevidenceofdistributionfrommoreimportantproductionsites,inspiteofacertainpopularitysuggestedbythehighpercentagesoffossiliferouspotteryamongtheceramicmaterialinthesettlements.

2.34

Insightsintothedehydroxylationkineticsoflizarditeandchrysotile

TrittschackRoy&GrobétyBernard

University of Fribourg, Department of Geosciences, Chemin du Musée 6, CH-1700 Fribourg ([email protected])

Lizardite and chrysotile represent two prominent trioctahedral 1:1 phyllosilicates of the serpentine mineral group.Lizardite(Mg3Si2O5(OH)4)hasaconventionalsheetsilicatestructure,whereasinchrysotilethesameTO-layersarerolledtocylinders.Thechrysotile structurehas thusnota classical3D-symmetry,butonly rotational andno radial symmetry.Physicalpropertiesare,therefore,expectedtoreflectalsothisnon-conventionalsymmetry.

Theaimofthisstudyistounderstandtheinfluenceofspecialsymmetryofchrysotileonthemechanismandtheratedeterminingstepsofthedehydroxylationreaction.Thedehydroxylationkineticsoflizarditeserves,thereby,asreference.

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Theoretical deprotonation andwater forming schemeswere comparedwith results of in-situHigh-TemperatureX-raydiffraction,in-situIR-spectroscopy,FTIRandDifferentialThermogravimetryexperimentsonwellcharacterizedchrysotileandlizarditesamples.In-situIRandHT-XRDexperimentsunderambientpressuregavestartingtemperaturesforthede-hydroxylationoflizaditebetween500°Cand550°Cwhichliesintherangeofformerinvestigations(Franketal.2005).

Chrysotiledehydroxylationdependonstructuralfeaturesliketheinnerandoutertubediameterwhichitselfdictatethephysicalproperties.Thedehydroxylationstartsattheoutermostlayersataround450°Cand500°C,whereasinnermostlayers breakdownabout600°C (Metraux et al. 2002). The initial dehydroxylationproduct of bothpolymorphs isX-rayamorphous,butcrystallizesafteracertain timeto forsterite.Thesephase transformationswerealso followedbyFTIRanalyses,whichofferadetailedinsightintothestructuralrecombinationduringthedehydroxylation.

Kineticdatawerecalculatedfromtwoindependentmethods,in-situHigh-TemperatureX-raydiffractionandDifferentialThermogravimetrytechniquesfordifferentatmospheres(N2,O2,air,etc.).Assumingproportionalitybetweentheintegralintensityofdiffractionpeaksandtheamountofserpentinepresent,thereactionratecanbeextractedfromtherateofintensitydecrease.Data from isothermal runshavebeen treatedwith theconventionalAvramimethodaswellas the“timetoagivenfraction”(TGF)method.LatteroneoffersthepossibilitytodiscoverchangesintheactivationenergyEaduringthecourseofdehydroxylation(Putnis1992).ThesamereactionprogressdependencyofEacanalsobeobtainedbytheisoconversionalFriedmananalysisfromaseriesofdynamicDTGdata.

IsothermalHT-XRDexperimentsonlizarditeyieldedEaofaround340kJmol-1(Avramimethod).DatatreatedwiththeTGFmethodshowedaprogressiveincreaseoftheEawiththefractiontransformedfromaround200kJmol-1(α=0.1)to340kJmol-1(α=0.9).Non-isothermalDTGanalysesonlizarditewithdifferentheatingratesandunderacontrollednitrogenat-mosphere confirmed the TGF results and enabled amuchmore detailed resolution of the Ea during the dehydrationprogress.Apreliminarymechanisticinterpretationoftheseresultswillbegiven.

REFERENCESFrank,M.R.,Earnest,D.J.,Candela,P.A.,Wylie,A.G.,Wilmot,M.S.&Maglio,S.J.2005(abstract):Experimentalstudyof

thethermaldecompositionoflizarditeupto973K,SaltLakeCityAnnualMeeting2005Metraux,C.,Grobéty,B.&Ulmer,P.2002:Fillingofchrysotilenanotubeswithmetals,JorunalofMaterialResearch,17,

1129-1135.Putnis,A.1992:IntroductiontoMineralSciences,CampridgeUniversityPress,457p.

2.35

Calculatingrheologicpropertiesofmagmasfromfieldobservationscom-binedwithexperimentaldata.

VerberneRoel1,UlmerPeter2,MüntenerOthmar1

1 Institut de Minéralogie et Géochimie, batiment Anthropole, CH-1015 Lausanne ([email protected]) 2 Institut für Geochemie und Petrologie, Clausiusstrasse 25, CH-8092 Zürich

Inordertoinvestigatetheemplacementprocessesthatoccurinshallowlevelplutonicmagmareservoirs,wetrytorelatephaseassemblagesandmineralcompositiontotheemplacementhistoryofaparticularrocksuitebycombiningfieldandexperimentalapproachestounderstandthephysical,rheologicalandtemporalevolutionofcrystallizingbatholiths.

HerewepresentacasestudyoftheListinoRingStructureoftheAdamelloBatholith,N-Italy,whereprocessesofinterac-tionbetweenfelsicandmaficmagmas,suchasmaficdikeinjectioninpartlycrystallizedsilicicmagmas,dikedisaggrega-tion,enclaveformation,andnear-solidusshearingwerestudiedinglacier-polishedoutcrops.Mostofthesephenomenaaregenerallyassignedtof luiddynamicprocessesoperatinginamagmareservoir(Turner&Campbell,1986),whererheolo-gicalbarriers(e.g.viscositycontrast)inhibitchemicalmixingofmaficmagmaswithcrystal-richsilicicmagmas(Sparks&Marshall,1986;Blundy&Sparks,1992).

Ourapproachcentersaroundthedeterminationofmineralassemblagesandcrystalfractionspresentatthetimeoftheprocessunderinvestigation.Themineralassemblageatthetimeofinjectionofmaficmagmas,canbedeterminedfromtheobservationthatmineralsfromthehostmagmaarebeingmechanicallyincorporatedasphenocrystsintothe

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maficenclavesbeforequenchingoccurs.Inthecaseofsynmagmaticdeformation,thecrystalspresentduringdeformationcanpossiblybeidentifiedbydeterminingthecrystalfractiondisplayingplasticdeformation.

Havingdeterminedthemodalmineralogyandcompositionofphases,combiningwithwholerockchemistryofbothmag-masandapressureestimateobtainedfromAl-in-HornblendebarometrybyBlundy&Caddick(unpublished),allowsustoconstrainthetemperatureandH2O-contentofthehostmagma.Themeltfractionandcompositionofthehostmagmacanthenbecalculatedfromavailableexperimentaldata,andthemeltcompositioncanbefurtherconstrainedbythechemicalanalysisofassemblagesfoundin(back)veins,whicharethoughttorepresentthemeltcomponentofthesystem.

Observedcrosscuttingrelationshipsbetweenthedifferentmagmaticphasescombinedwiththeirrespectiveoffsetalongsynmagmaticshearzonescanbeusedtodeterminestrainandpossiblystrainratesthroughdatingofthevariousphases.Havingdeterminedthecomposition,pressure,temperatureandcrystallinityofthehostmagma,itsrelativeviscositycanbecalculatedusingtheexperimentallycalibratedrelationshipbetweenrelativeviscosityandtheparticlevolumefraction(Costaetal.,2009andreferencestherein).

REFERENCESBlundy,J.D.andSparks,R.J.S.,1992.PetrogenesisofmaficinclusionsingranitoidsoftheAdamelloMassif,Italy.Journal

ofPetrology,33:1039-1104.Costa,A et al., 2009.Amodel for the rheologyof particle-bearing suspensions andpartiallymolten rocks.Geochem.

Geophys.Geosyst.,10,Q03010,doi:10.1029/2008GC002138.Sparks, R.S.J. andMarshall, L.A., 1986. Thermal andmechanical constraints onmixing betweenmafic and silicic

magmas.J.volc.geotherm.res.,29:99-124.Turner,J.S.andCampbell,I.H.,1986.Convectionandmixinginmagmachambers.Earth.Sci.Rev.,23:255-352.

2.36

Howlongdoesseawaterandoceaniccrustinteract?

FlurinVils1,TimElliott1,ChristopherE.Smith-Duque2,JeffreyC.Alt3&DamonTeagle2

1 University of Bristol, BS8 1RJ Bristol, United Kingdom (1 correspondence: [email protected])2 National Oceanography Centre, SO14 3ZH Southampton, United Kingdom3 University of Michigan, MI 48109-1005, USA

Afterhavingbeenformedatmid-oceanridges,oceanicplatescoolastheymoveawayfromtheridgesandbecomeolder.Muchofthiscoolingisrelatedtohydrothermalalterationbyseawaterinfiltratingtheplates.Duringseawater-rockinter-action,primarymineralsaretransformedintosecondaryminerals.Thistransformationcanmobilizeelements,whichareleachedoforenrichedintheoceaniccrustandisthereforeinfluencingthebulkrockcomposition.

Twoprocessesmainlycontrolelementabundancesintheoceans:continentalweatheringandhydrothermalactivityintheoceanicplate.Thehydrothermalactivity is furtherdividedintohigh-T (nearridge)andlow-T (offtheridge)alteration.High-Talterationprocessescanbeeasilystudiedinhydrothermalventregions.Aslow-Talterationprocessesintheoceaniccrustareratherdiffuseandslow,therelimitsandconditions(time,temperature,etc.)arelargelyunknownandthusin-vestigationofoff-ridgealterationisimportant.Thisstudyinvestigatesthealterationprocessesofmid-oceanridgebasalts(MORB)inthelow-Tenvironmentsandconstructsatimeframeforseawater-rockinteractionintheseregions.

WeatheringofthecontinentalplateskeeptheU-seriesdecaychainintheocean(a234U/238U-ratioof~1.14)indisequilibri-um.Ontheotherhand,MORBformedattheridgeareinsecularequilibrium.ThusanyseawateralterationofMORBleadstoanenriched234U/238U-ratioandafter~5half-lifetimesofuraniumtheMORBareagaininsecularequilibrium.Preliminary234U/238U-dataonoldoceaniccrustfromODPSite1179(~129Ma)andODPSite843(~94Ma)showsthatalteredMORBaremostlyinsecularequilibrium.Nevertheless,higherUconcentrationsinthealteredMORBcomparedtofreshMORBonbothSitessuggeststhatseawateralterationoccurredearlier,butoutsidetheradiogenicdetectionwindowof~1.25Maforthe234U/238Udecaychain.AlteredMORBfromyoungerODPSites(e.g.ODPSite1301,~3.5Ma)showdisequilibrium,repre-sentingrecentseawater-rockinteractions.AdditionalU-seriesmeasurementsonODPSitesarecurrentlyproceedtofurtherconstrainthealterationtime-window.

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2.37

Bariumisotopefractionationinnaturalbariummineralsandprecipitati-onexperiments:Afirstglimpseattheglobalbariumcycle

KatjavonAllmen(1,3),MichaelE.Böttcher(2),EliasSamankassou(1,3),andThomasF.Nägler(4)

(1 ) Department of Geosciences, Chemin du Musée 6, University of Fribourg, CH-1700 Fribourg, Switzerland ([email protected]),(2 ) Leibniz Institute for Baltic Sea Research (IOW), Geochemistry & Isotope Geochemistry Group, D-18119 Warnemünde, FGR ([email protected]),(3 ) present address: Section of Earth and Environmental Sciences, University of Geneva, Rue des Maraîchers 13, CH-1205 Geneva, Switzerland ([email protected]),(4 ) Institute of Geological Science, Baltzerstr. 3, University of Bern, CH-3012 Bern, Switzerland ([email protected])

Wepresentresultsfromanongoinginvestigationonthestablebarium(Ba)isotopefractionationinthenaturalBacycle.StableBaisotopesignaturesofinternationalIAEAreferencematerials(syntheticbariumsulfateandbariumcarbonate),naturalBamineralsandBaprecipitateshavebeenanalyzedtoevaluatepotentialdiscriminatingprocessesintheglobalgeochemicalbariumcycle.

Inthemodernocean,dissolvedBarium(Ba)showsavariableconcentrationandanutrient-typebehavior(Chanetal.,1976).Asanon-conservativeelement,Bahasarelativelyshortresidencetimeof11kyrs(Edmondetal.,1979).Baconcentrationsarereduced in theupperwatersof theopenoceanandenriched indeepwatersandareasofnutrientupwelling (e.g.,Church,1979).VariationsintheaccumulationrateofBaboundtocarbonateandsulfateinmarinesedimentsarethoughttobeindicativeofvariationsinmarinebiologicalproductivitythroughtime(e.g.,Church,1979;Paytan&Griffith,2007).DetritalsourcesofBafromcontinentalrunoff,hydrothermalalteration,anddiageneticBamobilityarehardtoconstrainwithBaconcentrationsalone.Thus,weproposethefractionationofstableBaisotopesasanewtooltoconstrainBabeha-viorintheglobalelementcycle.

Measurementswerecarriedoutonamulti-collectorICP-MSapplyinga130Ba/135Badoublespike.DataaregivenaspermildeviationsfromalaboratoryBanitratestandardsolutioninthed137/134Banotation(external2sstdev<0.1permil).Varioussyntheticsolidstandardsandthep.a.qualitysyntheticbariumchlorideusedfortheprecipitationexperimentsshowverysimilar isotoperesultsclosetothenitratestandardsolution.Theterrestrialbariumgangueminerals (fourbarites,onenorsethite[BaMg(CO3)2])weredepletedintheheavyisotope(d

137/134Baavaluesbetween0and-0.2permil).

AnaturalbaritefromanundisclosedChineselocalitygaveanisotopevalueof-0.4permil.High34S/32Sand18O/16Oratiosin this sample indicate that thisbaritehasbeenformedunder influenceofmicrobial sulfatereduction,probably inamarinediageneticenvironment.ThelargestBaisotopefractionationwith-0.5permilwasfoundinadiageneticbarite.Thisvalueisalsoaccompaniedbyhigh34S/32Sand18O/16Oratiosindicatingformationunderinfluenceofmicrobialsulfatereduction.Theobservednaturaldiscriminationsarebyfarlargerthantheanalyticaluncertaintyoftheisotopemeasure-ments,indicatingisotopediscriminationinthenaturalbariumcycle(vonAllmenetal.,2010).

Precipitationexperimentsfromaqueousbariumchloridesolutionsattemperaturesof20°and80°CindicatethatthelightBaisotopeisenrichedinpurebariumcarbonateorbariumsulfatecomparedtotheaqueoussolution.Amaximumisotopefractionationof-0.3permilisobserved,forbothbariumcarbonateandsulfate.Thisfractionationseemstobeinfluencedbyprecipitationrate(BaCO3)and/ortheaqueousspeciation,butlessbytemperature.

REFERENCES:Chan,L.H.,Edmond,J.M.,Stallard,R.F.,Broecker,W.S.,Chung,Y.C.,Weiss,R.F.&Ku,T.L.,1976:Radiumandbariumat

GEOSECSstationsintheAtlanticandPacific.EarthPlanet.Sci.Lett.,32,258-267.Church,T.M.,1979:Marinebarite,inBurns,R.G.(Editor),Marineminerals.MineralogicalSocietyofAmerica,Reviewsin

Mineralogy,6,175–209.Edmond,J.M.,Measures,C.,McDuff,R.E.,Chan,L.H.,Collier,R.,Grant,B.,Gordon,L.I.&Corliss,J.B.,1979:Ridgecrest

hydrothermalactivityandthebalancesofthemajorandminorelementsintheocean-Galapagosdata.EarthPlanet.Sci.Lett.,46,1-18.

Paytan,A.&Griffith,E.M.,2007:Marinebarite:Recorderofvariationsinoceanexportproductivity:Deep-SeaResearch:PartII,TopicalStudiesinOceanography,doi:10.1016/j.dsr2.2007.01.007.

vonAllmen,K.,Böttcher,M.E.,Samankassou,E.,&Nägler,T.F.,(2010):Bariumisotopefractionationintheglobalbariumcycle: First evidence frombariumminerals and precipitation experiments. Chem.Geol., (in press) doi:10.1016/j.chemgeo.2010.07.011

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2.38

PalaeoredoxchangeduringOAE1a:newinsightsfromphosphorusandredox-sensitivetraceelements

StéphaneWestermann1,MelodyStein2,VirginieMatera3,NicolasFiet4,ThierryAdatte2&KarlB.Föllmi2

1 Department of Earth Sciences, University of Bristol, Wills Memorial, BS81RJ, Bristol, UK ([email protected])2 Institut de géologie et de paléontologie, Université de Lausanne, CH-1015, Lausanne, Switzerland3 I.N.R.S., Avenue de Bourgogne, 54500 Vandoeuvre-les-Nancy, France4 AREVA, 33 rue La Fayette, 75442 Paris, France

TheEarlyAptianrecordsanepisodeofsevereenvironmentalchangeincludinganoceanicanoxicevent(OAE),aplatformdrowningepisodeandabiocalcificationcrisis.Thisepisode,theso-calledOAE1a,correspondstooneofthemoststudiedanoxiceventsand ischaracterizedbyan increase inthed13Cvaluesprecededbyanegativespike.Here,weproposetotracechangesinoceanchemistryduringOAE1atoimproveourunderstandingofsuchphenomenaandtesttheproposedmodels.Thus,we investigatephosphorus (P) and redox-sensitive trace-element (RSTE)distributions in sections alongabasin-shelftransectinthewesternTethysthroughlowerAptiansediments.Wecomplementourgeochemicalanalysisbytheanalysisoforganic-mattercontents.

Weselectedthreerepresentativesections:GorgoaCerbara(centralItaly)intheUmbriaMarchebasin,Glaise(SEFrance)locatedintheVocontianTroughandCassis/LaBédoule(SEFrance)locatedalongtheProvencalplatform.

InthesectionsofGlaiseandCassis/LaBédoule,PcontentsshowfirstanincreaseattheonsetoftheEarlyAptianevent,justabovethed13Cnegativespike,andthen,duringtheOAE1a,followedbylowervalues.Asecondincreaseisobservedattheendofthecarbon-isotopicexcursion.Thissuggestsanincreaseinnutrientinput,whereasthereturntolowervaluesthroughthefirstpartoftheanoxiceventmayberelatedtoaweakenedcapacitytoretainPinthesedimentaryreservoirduetobottom-wateroxygendepletion.Thisgeneralpattern iscontrastedbythedataofGorgoaCerbara.Surprisinglyenough,thesedimentsdepositedduringtheOAE1a(theSellilevel)showsP-enrichments(mainlyauthigenicP)associatedwithmaximuminTOCvaluesandhighCorg:Ptotratios.ApartoftheremobilizedPappearstohavebeentrappedinthesedimentsandwasassuchpreventedfromreturningtothewatercolumn.

InthesectionofGorgoofCerbara,U,V,Mo,CoandAsdistributionspresentsimilarbehaviourwithalowbackgroundlevelalongthemainpartofthesection,contrastedbydifferentmaximainconcentrationswithintheSellilevel.IntheGlaisesection,aweakincreaseisobservedjustafterthenegativespikeind13CwhereasintheCassis/LaBédoulesection,nosignificantenrichmentshavebeenobservedinsedimentsequivalenttotheSellilevel.ThedifferentbehaviouroftheRSTEinthestudiedsectionsmayberelatedtothepalaeogeographicsettingofthestudiedsections.Ourdataseemtoin-dicatethedevelopmentofanoxicconditionsinbasinsettingsduringOAE1a.Inshallower-waterenvironments,conditionsmayhavebeenlessreducing.Moreover,inGorgoaCerbara,twodistinctenrichmentshavebeenobserved.Thisisinfavouroff luctuationsintheintensityofwater-columnanoxiaduringtheshiftind13C.

OurresultsshowthattheexpressionoftheOAE1aisdifferentfollowingthepalaeogeographicsettings.ThestratigraphicevolutionofPcontentssuggestsanincreaseinnutrientinputattheonsetoftheanoxicevent,justafterthenegativespikeind13C.RSTEandhighCorg:Ptotvaluesmayindicateanoxiaconditionsinthedeepenvironmentcharacterizedbyseveralanoxicphaseswithintermittentreturntolessoxygen-depletedconditions.Theserapidchangesinredoxconditionsmayberelatedtoaf luctuatingoxygen-minimumzoneandsuggestthatoceanicproductivityhasplayedakeyroleinbottom-wateroxygendepletionduringOAE1a.

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2.39

InfluenceofextrinsicweatheringfactorsonmineraldissolutioninDammaglacierforefield

WongfunNuttakan1,FurrerGerhard1,BrandlHelmut2&PlötzeMichael3

1 Inst. of Biogeochemistry and Pollutant Dynamics, ETH Zürich, Universitätstrasse 16, CH-8092 Zürich ([email protected])2 Inst. of Evolutionary Biology and Environmental Studies, Universität Zürich, Winterthurerstrasse 190, CH-8057 Zürich3 Inst. for Geotechnical Engineering, ETH Zürich, Schafmattstrasse 6, CH-8093 Zürich

Initialweatheringprocessesandsoilformationareofparticularinterestinalpinepostglacialareasduetotheircrucialroleonlifeunderharshconditions(Bernasconi&BigLinkprojectmembers2008).Atnear-neutralpHunderaerobiccon-ditions,theavailabilityofnutrientsinfine-grainedrockmaterialandsoilisusuallyverylow.Toovercomethislimitation,microorganismsandplantsmodifytheirlocalenvironmentbyvariousexudatesincludingorganicligands,siderophoresandalsocyanide.Cyanidecanbeaveryimportantagentduringtheinitialperiodofcolonizationandsoilformation.

Westudymechanismsofweatheringofprimaryrock-formingmineralsintermsofintrinsic(e.g.mineralogy,grain-size,surfacearea)andextrinsic (e.g.pH,Eh,concentrationsof ligands)weatheringfactors.RocksamplesandsamplesfromweatheredstreamsedimentswereobtainedfromtheDammaglacierforefieldarea(CentralAlps,Switzerland)atapproxi-mately2000ma.s.l.Thestreamsedimentsampleswerecollecteddistinguishingfourwaterregimesregardingthedistancefromthemainwaterstreamandtheaccessibilityofwater.

MineralogicalcompositionsdeterminedbyX-raydiffractionandRietveldanalysisshowsimilarityinmineralogicalhetero-geneityofthemetagraniticmaterialthroughouttheglacierforefield.Grain-sizedistributionandaccordinglytheminera-logicalcompositionareinfluencedbyhydrologicalfactorssuchastemporalavailabilityandf lowvelocityofwater.Inadditiontofieldobservations,weatheringofcrushedgraniteisinvestigatedincontrolledlabexperiments.At25 °C,theinfluencesofoxalate,citrateandcyanidearestudiedinbatchreactors.Theconcentrationofcyanideismaintainedbyaconstantpartialpressureofhydrogencyanidethroughgasbubbling.Thus, theconcentrationofcyanideanionstrictlydependsonpH.Preliminaryresultsshowthatcitrateexhibitsthemostdistincteffectandthepresenceofcyanidesup-pressedthemobilizationofiron.

REFERENCESBernasconi, S.M. andBigLinkprojectmembers. 2008:Weathering, soil formationand initial ecosystemevolutionona

glacierforefield:acasestudyfromtheDammaGlacier,Switzerland.MineralMag.72,19-22.

2.40

Water-solublesaltsandtemperaturevariationinmeteoritesrecoveredinthehotdesertofOman

ZurfluhFlorian1,HofmannBeda2,GnosEdwin3&EggenbergerUrs1

1 Institut für Geologie, Baltzerstrasse 1+3, CH-3012 Bern ([email protected])2 Naturhistorisches Museum Bern, Bernastrasse 15, CH-3005 Bern 3 Muséum d’Histoire naturelle, route de Malagnou 1, CP 6434, CH-1211 Genève

OneofthemajorgoalsofourlongstandingmeteoritesearchandresearchcollaborationbetweentheMinistryofCommerceandIndustry,SultanateofOmanandinstitutionsfromSwitzerlandistocollectastatisticalsignificantnumberofwelldocumentedmeteoritesamplestoperformstudiesonfinddensity(Gnosetal.2010),weatheringandcontamination(Al-Kathirietal.2005).Herewepresentanongoingstudyontheinteractionofordinarychondriteswiththedesertsoilwiththefocusonwater-solublesalts.

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Duringterrestrialresidencethecomponentsfirstattackedinanordinarymeteoritearetheironmineralskamaciteandtaeniteandthe ironsulfidetroilite (Wlotzka1993,Lee&Bland2004,Al-Kathirietal.2005).Besideoxygen,waterandmicrobes,saltsderivedfromthesoilaccelerateweatheringofthesemineralsinthemeteorite.Chlorineisanimportantconstituentinvolvedintheformationoftheironhydroxideakaganéite(Buchwald&Clarke1989).

Afirstsurveyofwater-solublesaltsinmeteoritesgaveinterestingresults:Aqueousleachingwasperformedon16small(3–6g)cubesfromtheinteriorof200–400gindividualstones.WedetectedMg2+,Ca2+,SO4

2-andCl-asthemajorions.Thesignalisdominatedbyeitherchlorineorsulphate.Chlorine,calciumandapartofthesulphatearederivedfromthesoil,whereasmagnesiumandsomeofthesulphateisofmeteoriticorigin.Thetotalconcentrationofwater-solubleionsvariesfrom1860ppmto10500ppminthesolid(Zurfluh2008).

Currentlyweperformadditionalteststooptimizetheexperimentalsetupofaqueousleaching.Multiplecubesfromonemeteoritepiecewereleachedduringvarioustimeperiodstogetanideaofsaltsolubilityasafunctionoftime.Additionally,theexperimentwasperformedunderN2atmospheretopreventoxidationofironduringleaching.UntilnowallextractiondataarecollectedfromsamplesofthelargeJaH091strewnfield,acommonL5S2W2-4ordinarychondrite(Russeletal.2004,Gnosetal.2006,Zurfluh2008,Gnosetal.2010).

Theprocessof contaminationwith these salts isnotunderstood indetail.One importantparametermaybe thedailytemperature f luctuation that causesapumpingeffect.Wesuppose thatdue to thedarkcolour,meteoritesundergoamuchlargertemperaturerangecomparedtothesurroundingsoil.

Toobtaindataontemperaturevariations insideameteorite,asamplefromJaH091strewnfieldwasequippedwithathermocoupleconnectedwithatemperaturedataloggerandplacedinthedesert.Asecondtemperaturesensorwasplacedinanaluminiumdiscandburiedatadepthof30cminthesoil.TheexperimentwasrunfromJune2009untilJanuary2010.Currentlyanewloggeriscollectingdataatthesamelocationtocoverthewholeyear.ThehighesttemperatureinthemeteoritewasmeasuredinmidJulyreaching66.3°Candthedailymin-maxtemperaturedifferencesinthemeteoriteaverages34.3°C. Incontrast, themaximumtemperaturerecordedinthesoil is54.8°Candthedailyvariationaverages21.6°C.Thistemperaturevariationinthemeteoriteismaybeenoughtoproduceapumpingeffectthattransportsionssolvedinwaterintotheporespaceofthemeteorite(averageporosityofordinarychondrites:8.9±4.9%;Consolmagnoetal.2008).Waterisavailablefrommorningdewandthelowannualprecipitation,typically<40mmthatoccursnormallybetweenJanuaryandMarch(Fisher1994).Duringhotperiodsthewaterevaporatesandthesaltsremainsinthemeteorite.Becauseofthelongresidencetimeofthemeteoriteandthelargenumberofthesecycleshighconcentrationsofsaltsre-sults.

REFERENCESAl-Kathiri, A.,HofmannB.A., JullA. J. T., andGnos E. 2005:Weathering ofmeteorites fromOman:Correlation of

chemical/mineralogicalweatheringproxieswith14Cterrestrialagesandtheinfluenceofsoilchemistry,Meteoritics&PlanetaryScience,40,1215-1239.

BuchwaldV.F.andClarkeR.S.1989:CorrosionofFe-NialloysbyCl-containingakaganeite(beta-FeOOH)-TheAntarcticmeteoritecase.AmericanMineralogist74,656-667.

ConsolmagnoG.J.,BrittD.T.andMackeR.J.2008:Thesignificanceofmeteoritedensityandporosity.ChemiederErde-Geochemistry68,1-29.

FisherM. 1994:Another look at the variability of desert climates, using examples fromOman.Global Ecology andBiogeographyLetters4,79-87.

Gnos, E., EggimannM.R.,Al-KathiriA. andHofmannB.A. 2006: The JaH091 strewn field,Meteoritics& PlanetaryScience41Suppl.,A64

Gnos,E.,Hofmann,B.,Walbrecker,J.,Zurfluh,F.,Eggenberger,U.,Greber,N.,Opitz,C.,Bretscher,A.andTrappitsch,R.2010:„The2010OmanmeteoritesearchcampaignwithamagneticsurveyofthemainimpactsiteoftheJaH091strewnfield,AbstractSwissGeoscienceMeeting2010,Fribourg.

LeeM.R.andBlandP.A.2004:Mechanismsofweatheringofmeteoritesrecovered fromhotandcolddesertsandtheformationofphyllosilicates.GeochimicaetCosmochimicaActa68,893-916.

Russell S. S., Folco L., GradyM.M., ZolenskyM. E., Jones R., Rigther K., Zipfel J. andGrossmann J. N. 2004: TheMeteoriticalBulletin,No.88,2004July.Meteoritics&PlanetaryScience39,A215-A272.

WlotzkaF.1993:AWeatheringscalefortheordinarychondrites(abstract).Meteoritics28,460.ZurfluhF.J.2008:MeteoritesintheSultanateofOman-EffectsofterrestrialweatheringintheJiddatalHarasis(JaH)091

Strewnfield.MSc-thesis,UniversityofBerne,138pp.

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