微量元素地球化学中国地质大学4微量元素在不同地质体中的分布与分配课件

微量地球化学

TraceElementGeochemistry

“Geochemistryreallyisforeveryone!”

ByFersman(1958)4.微量元素在各主要地质体中的分布矿物岩石地球化学储库主要造岩矿物橄榄石单斜辉石斜方辉石石榴石尖晶石斜长石KdDatabaseSearchResultsRockTypeMineralZElementValueKdTypeReferenceBasaltOlivine3Li0.35ExperimentalNikogosian&Sobolev1997BasaltOlivine12Mg6.6ExperimentalKloeck&Palme1988BasaltOlivine22Ti0.007ExperimentalNikogosian&Sobolev1997BasaltOlivine24Cr0.73ExperimentalNikogosian&Sobolev1997BasaltOlivine26Fe1.85ExperimentalKloeck&Palme1988BasaltOlivine27Co3.1ExperimentalPasteretal.1974BasaltOlivine28Ni12.2Phenocrysts-MatrixBougault&Hekinian1974BasaltOlivine30Zn0.86Phenocrysts-MatrixBougault&Hekinian1974BasaltOlivine37Rb0.04Phenocrysts-MatrixVillemantetal.1981BasaltOlivine39Y0.009ExperimentalNikogosian&Sobolev1997BasaltOlivine40Zr0.06Phenocrysts-MatrixVillemantetal.1981BasaltOlivine56Ba0.03Phenocrysts-MatrixVillemantetal.1981BasaltOlivine57La0.0004CalculatedMcKenzie&O'Nions1991BasaltOlivine58Ce0.01ExperimentalPasteretal.1974BasaltOlivine59Pr0.0008CalculatedMcKenzie&O'Nions1991BasaltOlivine62Sm0.0013CalculatedMcKenzie&O'Nions1991BasaltOlivine63Eu0.0016CalculatedMcKenzie&O'Nions1991BasaltOlivine65Tb0.0015CalculatedMcKenzie&O'Nions1991BasaltOlivine66Dy0.007ExperimentalNikogosian&Sobolev1997BasaltOlivine67Ho0.0016CalculatedMcKenzie&O'Nions1991BasaltOlivine69Tm0.009Phenocrysts-MatrixFrey1969BasaltOlivine70Yb0.021ExperimentalNikogosian&Sobolev1997BasaltOlivine71Lu0.018Phenocrysts-MatrixFrey1969BasaltOlivine72Hf0.04Phenocrysts-MatrixVillemantetal.1981BasaltOlivine73Ta0.03Phenocrysts-MatrixVillemantetal.1981BasaltOlivine79Au0.7ExperimentalKloeck&Palme1988橄榄石橄榄石0.0010.010.1110100100010000Li7Al27Si29P31Ca42Sc45Ti49V51Cr53Co59Ni60Cu63Ga71Rb85Sr88Y89Zr90Nb93Cs133Ba137La139Ce140Pr141Nd143Sm147Eu151Gd155Tb159Dy163Ho165Er166Tm169Yb173Lu175Hf179Ta181Pb208Th232U238含量（ppm）0.00010.0010.010.1110LiScVCrCoNiCuGaRbSrYZrNbCsBaLaCePrNdSmEuGdTbDyHoErTmYbLuHfTaPbThU原始地幔归一化值0.00010.0010.010.1110100100010000LiScVCrCoNiCuGaRbSrYZrNbCsBaLaCePrNdSmEuGdTbDyHoErTmYbLuHfTaPbThU含量（ppm）斜方辉石0.0010.010.1110100LiScVCrCoNiCuGaRbSrYZrNbCsBaLaCePrNdSmEuGdTbDyHoErTmYbLuHfTaPbThU原始地幔归一化值RockTypeMineralZElementValueKdTypeReferenceBasaltClinopyroxene4Be0.047ExperimentalHart&Dunn1993BasaltClinopyroxene5B0.036ExperimentalHart&Dunn1993BasaltClinopyroxene19K0.0072ExperimentalHart&Dunn1993BasaltClinopyroxene21Sc0.808ExperimentalHaurietal.1994BasaltClinopyroxene22Ti0.229ExperimentalSobolevetal.1996BasaltClinopyroxene23V1.81ExperimentalHaurietal.1994BasaltClinopyroxene24Cr1.66ExperimentalHaurietal.1994BasaltClinopyroxene25Mn1.6ExperimentalPasteretal.1974BasaltClinopyroxene27Co1.3ExperimentalPasteretal.1974BasaltClinopyroxene28Ni2.6ExperimentalMysen1978BasaltClinopyroxene29Cu0.36ExperimentalHart&Dunn1993BasaltClinopyroxene30Zn0.49ExperimentalPasteretal.1974BasaltClinopyroxene31Ga0.74ExperimentalHart&Dunn1993BasaltClinopyroxene38Sr0.082ExperimentalSobolevetal.1996BasaltClinopyroxene39Y0.245ExperimentalSobolevetal.1996BasaltClinopyroxene40Zr0.046ExperimentalSobolevetal.1996BasaltClinopyroxene41Nb0.004ExperimentalJohnson1994BasaltClinopyroxene55Cs0.0058ExperimentalHaurietal.1994BasaltClinopyroxene56Ba0.002ExperimentalSobolevetal.1996BasaltClinopyroxene57La0.032ExperimentalSobolevetal.1996BasaltClinopyroxene58Ce0.057ExperimentalSobolevetal.1996BasaltClinopyroxene59Pr0.277ExperimentalHaurietal.1994BasaltClinopyroxene60Nd0.129ExperimentalSobolevetal.1996BasaltClinopyroxene61Pm0.462ExperimentalHaurietal.1994BasaltClinopyroxene62Sm0.211ExperimentalSobolevetal.1996BasaltClinopyroxene63Eu0.27ExperimentalPasteretal.1974BasaltClinopyroxene64Gd0.41ExperimentalPasteretal.1974BasaltClinopyroxene65Tb0.711ExperimentalHaurietal.1994BasaltClinopyroxene66Dy0.256ExperimentalSobolevetal.1996BasaltClinopyroxene67Ho0.66ExperimentalHaurietal.1994BasaltClinopyroxene68Er0.259ExperimentalSobolevetal.1996BasaltClinopyroxene69Tm0.633ExperimentalHaurietal.1994BasaltClinopyroxene70Yb0.214ExperimentalSobolevetal.1996BasaltClinopyroxene71Lu0.223ExperimentalHaurietal.1994BasaltClinopyroxene72Hf0.23ExperimentalJohnson1994BasaltClinopyroxene73Ta0.0102ExperimentalHaurietal.1994BasaltClinopyroxene82Pb0.014ExperimentalHaurietal.1994BasaltClinopyroxene90Th0.0127ExperimentalHaurietal.1994BasaltClinopyroxene92U0.06ExperimentalBenjaminetal.1978单斜辉石单斜辉石0.0000.0010.0100.1001.00010.000LiScVCrCoNiCuGaRbSrYZrNbCsBaLaCePrNdSmEuGdTbDyHoErTmYbLuHfTaPbThU原始地幔归一化值单斜辉石KdDatabaseSearchResultsRockTypeMineralZElementValueKdTypeReferenceBasaltGarnet21Sc2.62ExperimentalHaurietal.1994BasaltGarnet22Ti0.688ExperimentalHaurietal.1994BasaltGarnet23V1.48ExperimentalHaurietal.1994BasaltGarnet24Cr2.01ExperimentalHaurietal.1994BasaltGarnet28Ni5.1ExperimentalMysen1978BasaltGarnet38Sr0.0099ExperimentalHaurietal.1994BasaltGarnet39Y2.8ExperimentalJohnson1994BasaltGarnet40Zr2.12ExperimentalHaurietal.1994BasaltGarnet41Nb0.0538ExperimentalHaurietal.1994BasaltGarnet56Ba0.0007ExperimentalHaurietal.1994BasaltGarnet57La0.0164ExperimentalHaurietal.1994BasaltGarnet58Ce0.065ExperimentalHaurietal.1994BasaltGarnet60Nd0.363ExperimentalHaurietal.1994BasaltGarnet62Sm1.1ExperimentalHaurietal.1994BasaltGarnet63Eu2.02ExperimentalHaurietal.1994BasaltGarnet66Dy4.13ExperimentalHaurietal.1994BasaltGarnet68Er3.95ExperimentalHaurietal.1994BasaltGarnet70Yb3.88ExperimentalHaurietal.1994BasaltGarnet71Lu3.79ExperimentalHaurietal.1994BasaltGarnet72Hf1.22ExperimentalHaurietal.1994BasaltGarnet82Pb0.00012ExperimentalHaurietal.1994BasaltGarnet90Th0.00137ExperimentalHaurietal.1994BasaltGarnet92U0.00588ExperimentalHaurietal.1994石榴石0.010.1110LiScVCrCoNiCuGa原始地幔归一化值RbSrYZrNbCsBaLaCePrNdSmEuGdTbDyHoErTmYbLuHfTaPbThU石榴石斜长石问题1如果亏损地幔由Ol+Opx+Cpx+Gt+Sp组成，那么：元素Yb主要分布在哪些种矿物中？元素La主要分布在哪些种矿物中？元素Ni主要分布在哪些种矿物中？元素Zr主要分布在哪些种矿物中？问题2榴辉岩主要由Cpx+Gt组成，那么：元素Yb主要分布在哪种矿物中？元素La主要分布在哪种矿物中？元素Ni主要分布在哪种矿物中？元素Zr主要分布在哪种矿物中？如果该榴辉岩中除了Cpx+Gt以外，还发现少量磷灰石，那么上述元素的分布情况如何？主要岩石大洋中脊玄武岩（MORB）洋岛玄武岩（OIB）大陆溢流玄武岩（CFB）岛弧玄武岩（IAB）Mid-OceanRidgeBasalts(MORB)MORBChemistryMORB’saredominantlyolivinetholeiiteswithdistinctivelylowK2O(<0.2%).Allincompatibletraceelements(LREE,K,Rb,Cs,Ba,Pb,Sr,Th,U,Ce,Zr,Hf,Nb,Ta,andTi)aredepleted.NodepletioninHREEelementsindicatingrelativelyshallowmeltingwithinthespinelstabilityfield(<70depth).SrandNdisotoperatiosaredepletedindicatingadepleteduppermantlesourceregion.OceanicIslandBasalts(OIB)

OceanicIslandBasalts(OIB)OIBChemistryOIB’sarerangefromolivinetholeiitestohighlyalkalinebasaltswithrelativelyhighTiO2,Na2O,K2O,andP2O5.Allincompatibletraceelements(LREE,K,Rb,Cs,Ba,Pb,Sr,Th,U,Ce,Zr,Hf,Nb,Ta,andTi)areenrichedinOIBmagmaswithrespecttoMORBs.HREEelementsaredepletedindicatingdeepmeltingwithinthegarnetstabilityfield(>70-80depth).SrandNdisotoperatiosarerelativelyenrichedwithrespecttoMORBsindicatingundepleted(primitive)and/orenrichedmantlesourcecomponents.TypesofOIBMagmas1.Tholeiiticseries(dominanttype)“Shield-buildingstage”-tremendousoutpouringsoftholeiiticbasaltsTypesofOIBMagmas2.Alkalineseries(smallvolumes)“Post-shieldstage”-Waningactivity.Lavasaremorediverse,withalargerproportionofchemicallydifferentiatedmagmasStrongenrichmentinhighlyincompatibletraceelements(REE,LILE,HFSE)indicatingundepleted(primitive)and/or“enriched”mantlesourcesDepletioninHREEindicatingrelativelydeepmeltingdepths(>80km)，Why？OIBChemistryOIBs:87Sr/86Sr=0.7035to–0.710andNd=+5to-5,®primitiveand/orenrichedmantlesource(s)Figure14-6.AfterZindlerandHart(1986),Staudigeletal.(1984),Hamelinetal.(1986)andWilson(1989).OIBPetrogenesisAdiabaticdecompressionmeltingassociatedwithdeepupwellingofanomalouslyhot(+100-200°C)mantle.

Partialmeltinginitiated>100kmdepthwellwithingarnetstabilityfield(explainscommonHREEdepletion).Relativelyenrichedtraceelementandisotopesignaturesindicateenrichedmantlesourcecomponents.DMOIBContinentalReservoirsEMandHIMUfromcrustalsources(subductedOC+CCseds)OIBPetrogenesisContinentalFloodBasalts(CFB)LargeIgneousProvinces(LIPs)OceanicplateausSomeriftsContinentalfloodbasalts(CFBs)Figure15-1.ColumbiaRiverBasaltsatHatPoint,SnakeRiverarea.CoverofGeol.Soc.AmerSpecialPaper239.PhotocourtesySteveReidel.TectonicSettingofCFBsContinentalhotspotsColumbiaRiverPlateau–YellowstoneDeccanTrapsContinentalriftingParana-EntendekaCAMP–(CentralAtlanticMagmaticProvince)CFBChemistryCFB’saremostlytholeiiticandsimilartoOIBIncompatibletraceelementsandisotopesareenriched,likeOIBBUTshowmuchmorevariabilitytowardmoreenrichedcompositions.Distinctiveenrichmentsofthemosthighlyincompatibleelements(K,Ba,Rb,Th,Pb,andLREE)overtypicalOIB.NoticeabledepletionsinHFSE(Nb,Ta)comparedtoOIB.SrandNdisotoperatiosoverlapwithOIB,butextendtomoreenrichedcompositions(higher87Sr/86SrandlowerNd).CFBChemistryStrongenrichmentsinhighlyincompatibletraceelements(REE,LILE)indicatingenrichedmantlesource(s)NodepletioninHREEindicatingrelativelyshallowmeltingdepths(<70km)DistinctiveernirchmentsinBaandPbanddepletionsinHFSE(Nb,Ta)comparedtoOIB.CFBs:87Sr/86Sr=0.7035to0.713andNd=+5to-10,®enrichedmantlesource(s)CFBPetrogenesisBasicallyOIBpetrogenesis+addedcomponentsfromcontinentallithosphericmantleandcrustFigure15-14.Diagrammaticcrosssectionillustratingpossiblemodelsforthedevelopmentofcontinentalfloodbasalts.DMisthedepletedmantle(MORBsourcereservoir),andtheareabelow660kmdepthisthelessdepleted,orenrichedOIBsourcereservoir.Winter(20010AnIntroductiontoIgneousandMetamorphicPetrology.PrenticeHall.MantleSourcesandStructureUpperdepletedmantle=MORBsourceLowerundepleted&enrichedOIBsourceOcean-oceanIslandArc(IA)Ocean-continentContinentalArcorActiveContinentalMargin(ACM)Figure16-1.Principalsubductionzonesassociatedwithorogenicvolcanismandplutonism.Trianglesareontheoverridingplate.PBS=Papuan-Bismarck-Solomon-NewHebridesarc.AfterWilson(1989)IgneousPetrogenesis,AllenUnwin/Kluwer.岛弧玄武岩(IAB)StructureofanIslandArcFigure16-2.SchematiccrosssectionthroughatypicalislandarcafterGill(1981),OrogenicAndesitesandPlateTectonics.Springer-Verlag.HFU=heatflowunit(4.2x10-6

joules/cm2/sec)TheSubductionFactoryRawmaterialsOceanicmaterialMantlematerialProductsMagma/VolcanoesVolatilesContinentalcrustResiduesChemicallymodifiedslabDelaminatedlowercrustMaterialRecyclingintheEarthInteriorSubductionProductsCharacteristicigneousassociationsDistinctivepatternsofmetamorphism

Orogenyandmountainbelts

ComplexlyInterrelatedMajorElementsandMagmaSeriesTholeiitic(MORB,OIT)Alkaline(OIA)Calc-Alkaline(~restrictedtoSZ)地球化学储库大陆总地壳(BCC)ByRudnickandGao(2003)Comparisonofcontinentalcrustandvariousbasalts

(Hoffmann,1994)Continentalcrust

LaCePrNdSmEuGdTbDyHoErTmYbLu110100Rock/ChondriteGaoetal.(1998;Eu/Eu*=0.80)Wedepohl(1995;Eu/Eu*=0.83)Rudnick&Fountain(1995;Eu/Eu*=0.98)Taylor&McLennan(1995;Eu/Eu*=1.00)TotalContinentalCrustTheSubductionFactoryRawmaterialsOceanicmaterialMantlematerialProductsMagma/VolcanoesVolatilesContinentalcrustResiduesChemicallymodifiedslabDelaminatedlowercrustLaCePrNdSmEuGdTbDyHoErTmYbLu110100Rock/ChondriteLaCePrNdSmEuGdTbDyHoErTmYbLu110100Rock/ChondriteLaCePrNdSmEuGdTbDyHoErTmYbLu110100Rock/ChondriteLaCePrNdSmEuGdTbDyHoErTmYbLu110100Rock/Chondrite

Mantle

NewcrustaladditionsLowercrustUppercrust

IntracrustalClasticsedimentsDifferen-tiationEuanomalyasaprobeforcrustalevolutionandlowercrustdelaminationLaCePrNdSmEuGdTbDyHoErTmYbLu110100Rock/ChondriteTotalcrustafterdelami-ationDelaminationEuEuEuEuEu地壳中元素的分布极不均一。除了不同元素的丰度显著变化外，元素分布在空间和时间上也都是不均一的；少数元素在数量上起决定作用，大部分元素居从属地位。前九种元素(O、Si、Al、Fe、Ca、Na、K、Mg、Ti)占98.13%，而前五种元素占了82.58%。地壳中元素丰度不是固定不变的，它是不断变化的开放体系；地球表层H、He等气体元素逐渐脱离地球重力场；每天降落到地球表层的地外物质102~105吨；地壳与地幔的物质交换；放射性元素衰变；人为活动的干扰。大陆地壳含有总硅酸岩地球中的大部分不相容元素(33-35%ofRb,Ba,K,Pb,ThandU)；相对亏损Nb、富集Pb；地壳、总地球和太阳系元素丰度的排序不同：太阳系：H>He>O>Ne>N>C>Si>Mg>Fe>S地球：Fe>O>Mg>Si>Ni>S>Ca>Al>Co>Na地壳：O>Si>Al>Fe>Ca>Na>K>Mg>Ti>H地壳元素分布的不均一性整个地球元素分布是不均匀的，这与壳、幔物质分异的整体过程相联系。地壳作为地球的组成部分，其元素的分布在空间和时间上也都是不均一的。1.空间上分布的不均一性垂向深度（陆壳）上地壳是花岗质的(SiO2=66%)，有明显Eu负异常；中地壳是英云闪长质的(SiO2=61%)；下地壳以基性(~52%SiO2)为主，一些克拉通和碰撞带具有更演化的成分Ri=上地壳元素丰度/下地壳元素丰度Ri约等于1:Ca,Si,Zr,Nd,Pb等Ri<1:Mg,Cu,V,Fe,Ni,Cr,Ag,Co,Sr等Ri>1:Cl,C,Cs,K,Rb,U,Th,Bi,Tl,Nb等反映了地壳物质在分异调整过程中的宏观趋势。横向分布洋壳：占地球表面60%以上，厚5-16km，它们的化学成分与地幔物质相似，以镁、铁硅酸盐为主，主要分布着Cr,Fe,Ni,Pt等亲铁元素。陆壳：占地球表面30%，厚30-50KM，它们的化学成分由铝、钾硅酸盐组成，主要分布着亲氧及亲硫元素W，Sn，Mo,Cu,Pb,Zn,Ag等。陆壳内：板块间、区域间、地质体间、岩石间、矿物间元素分布不均一性。

2.时间上地壳元素分布的不均一性（1/2）随着地质历史的发展，元素的活动与分布有着明显的规律性。地史早期：一些稳定元素在地史早期富集。Au元素：主要产在前寒武纪。Fe元素:主要产在前寒武纪元古代（前寒武纪变质铁矿占世界铁矿储量60%）。地史晚期：一些活泼的不稳定元素向着地史晚期富集