Elementos_tracos

Elementos MaioresElementos Maiores

Diferentes Elementos tem Diferentes Elementos tem diferentes afinidades no diferentes afinidades no ambiente que residem.ambiente que residem.

Si02 – aumenta Si02 – aumenta concentração com concentração com cristalização cristalização

Figure 8-2. Harker variation diagram for 310 analyzed volcanic rocks from Crater Lake (Mt. Mazama), Oregon Cascades. Data compiled by Rick Conrey (personal communication). From Winter (2001) An From Winter (2001) An Introduction to Igneous and Metamorphic Introduction to Igneous and Metamorphic Petrology. Prentice Hall.Petrology. Prentice Hall.

Elementos TraçosElementos Traços

Note a magnitude na mudança Note a magnitude na mudança dos elementos traçosdos elementos traços

Não formam minerais próprios, Não formam minerais próprios, sendo incorporados por outros. sendo incorporados por outros.

1 ppm = 1g/1 x 101 ppm = 1g/1 x 1066g =1mg/lg =1mg/l1 ppb =1g/1x 101 ppb =1g/1x 1099 g=10 g=10-3-3 ppm ppm= 1ug/l= 1ug/l

Figure 9-1.Figure 9-1. Harker Diagram for Crater Lake. From data Harker Diagram for Crater Lake. From data compiled by Rick Conrey. From Winter (2001) An Introduction compiled by Rick Conrey. From Winter (2001) An Introduction to Igneous and Metamorphic Petrology. Prentice Hall.to Igneous and Metamorphic Petrology. Prentice Hall.

some elements metals"Siderophile" Fe, Pt, Mo

some elements sulfides "Chalcophile" S,Cu,Zn

some elements silicates "Lithophile" Si,K,Ca,REE

Distribuição dos ElementosDistribuição dos Elementos

Regras de Goldschmidt (simples, mas usual)Regras de Goldschmidt (simples, mas usual)1.1. Dois ions com a mesma valência e raio podem Dois ions com a mesma valência e raio podem

facilmente ser trocados e participar de facilmente ser trocados e participar de soluções solidas em quantidades iguais em soluções solidas em quantidades iguais em todas as proporções.todas as proporções.

Como se comporta o Rb? Ni?Como se comporta o Rb? Ni?

Rb segue o K = concentra em KF, MicasRb segue o K = concentra em KF, Micas

Ni segue o Mg = concentra em OlNi segue o Mg = concentra em Ol

Goldschmidt’s rulesGoldschmidt’s rules

2. Se dois ions tem um raio similar e a mesma valência: 2. Se dois ions tem um raio similar e a mesma valência: O ion menor é preferentialmente incorporado no O ion menor é preferentialmente incorporado no

sólido sobre o líquido. (Mg é menor do que Fe, logo sólido sobre o líquido. (Mg é menor do que Fe, logo tem mais Mg na Ol do que no fundido tem mais Mg na Ol do que no fundido

Fig. 6-10. Isobaric T-X phase diagram at atmospheric pressure After Bowen and Shairer (1932), Amer. J. Sci. 5th Ser., 24, 177-213. From Winter From Winter (2001) An Introduction to (2001) An Introduction to Igneous and Metamorphic Igneous and Metamorphic Petrology. Prentice Hall.Petrology. Prentice Hall.

3. Se dois ions tem um raio similar, mas didferente valência: O ion com mais alta carga é preferencialmente incorporado no sólido sobre o líquido.

4. Cr +3 e Ti +4 são sempre preferidos no liquido/solido

Fracionamento QuímicoFracionamento Químico

A distribuição desigual de um ion entre A distribuição desigual de um ion entre duas fases competindo (equilibrio)duas fases competindo (equilibrio)

Transferência de equilibrio de um Transferência de equilibrio de um componentecomponente ii entre duas entre duas fasesfases (solido e liquido) (solido e liquido)

ii (liquid)(liquid) = = ii (solid)(solid)

eq. 9-2eq. 9-2 K = =K = =

K =K = constante de equilibrioconstante de equilibrio

a a solidsolid

a a liquidliquid iiii

XX solidsolid

XX liquidliquidii

ii

ii

ii

A concentração de Elementos traços segue A concentração de Elementos traços segue a Lei de Henry, em que sua atividade varia a Lei de Henry, em que sua atividade varia numa relação direta com sua concentração numa relação direta com sua concentração no sistemano sistema

Assim se a XAssim se a XNiNi no sistema duplica , a X no sistema duplica , a XNiNi

em todas as fases serão duplicadas em todas as fases serão duplicadas Isto não significa que a Isto não significa que a XXNiNi em todas as em todas as

fases é a mesma, já que os elementos fases é a mesma, já que os elementos traços vão fracionar s. Tanto quanto a traços vão fracionar s. Tanto quanto a XXNiNi dentro cada fase irá variar na dentro cada fase irá variar na

proporção da concentração do sistemaproporção da concentração do sistema

Por exemplo: supor

C(Ni) = 20 ppm no sistema

C(Ni) na olivina deve ser 100 ppm

C(Ni) no plagioclasio deve 1 ppm

C(Ni) no liquido deve ser 10 ppm

Duplicando C(Ni) no sistem para 40 ppm: Ol -> 200 ppm, Plag -> 2 ppm e liquido -> 20 ppm

Elementos incompativel Elementos incompativel são concentrados são concentrados no fundido (liquido)no fundido (liquido)

(K(KDD or D) « 1 or D) « 1

Elemento compativel Elemento compativel são concentrados no são concentrados no solido (mineral) solido (mineral)

KKDD or D » 1 or D » 1

Sendo que a concentração de elemento traço Sendo que a concentração de elemento traço (diferente dos maiores -note Fo-Fa) em uma (diferente dos maiores -note Fo-Fa) em uma fase é proporcional a concentração do elemento fase é proporcional a concentração do elemento envolvido, uma constante mais conveniente é envolvido, uma constante mais conveniente é usado para isto. Ela e comumente referida usado para isto. Ela e comumente referida como "D" (embora muitos autores permaneçam como "D" (embora muitos autores permaneçam usando KD) e é chamada de usando KD) e é chamada de coeficiente de coeficiente de partição partição ::

Para soluções diluidas pode substituir D por Para soluções diluidas pode substituir D por KKDD::

D =D =

Onde COnde CS S = e a concentração de um = e a concentração de um

elemento na fase sólidaelemento na fase sólida

(O valor é dado em wt% ou ppm diretamente). Se o elemento ocorre em uma fase muito diluida, D é uma constante.

CCSS

CCLL

Elementos Incompativeis Elementos Incompativeis Dois subgrupos Dois subgrupos

Elementos de alto campo elétrico, carga grande Elementos de alto campo elétrico, carga grande high field strength (HFS)high field strength (HFS) elementselements (REE, Th, U, (REE, Th, U, Ce, PbCe, Pb4+4+, Zr, Hf, Ti, Nb, Ta) = primeiro a , Zr, Hf, Ti, Nb, Ta) = primeiro a cristalizar e ultimo a fundir. Concentra em cristalizar e ultimo a fundir. Concentra em acessóriosacessórios

Elementos com baixa potencia de carga, elementos Elementos com baixa potencia de carga, elementos grandes grandes large ion lithophile (LIL)large ion lithophile (LIL) elements elements (K, (K, Rb, Cs, Ba, PbRb, Cs, Ba, Pb2+2+, Sr, Eu, Sr, Eu2+2+)) são mais moveis, são mais moveis, particularmente se uma fase fluida é envolvida, particularmente se uma fase fluida é envolvida, sendo extraido em qualquer processo.sendo extraido em qualquer processo.

Table 9-1. Partition Coefficients (CS/CL) for Some Commonly Used Trace

Elements in Basaltic and Andesitic Rocks

Olivine Opx Cpx Garnet Plag Amph MagnetiteRb 0.010 0.022 0.031 0.042 0.071 0.29 Sr 0.014 0.040 0.060 0.012 1.830 0.46 Ba 0.010 0.013 0.026 0.023 0.23 0.42 Ni 14 5 7 0.955 0.01 6.8 29Cr 0.70 10 34 1.345 0.01 2.00 7.4La 0.007 0.03 0.056 0.001 0.148 0.544 2Ce 0.006 0.02 0.092 0.007 0.082 0.843 2Nd 0.006 0.03 0.230 0.026 0.055 1.340 2Sm 0.007 0.05 0.445 0.102 0.039 1.804 1Eu 0.007 0.05 0.474 0.243 0.1/1.5* 1.557 1Dy 0.013 0.15 0.582 1.940 0.023 2.024 1Er 0.026 0.23 0.583 4.700 0.020 1.740 1.5Yb 0.049 0.34 0.542 6.167 0.023 1.642 1.4Lu 0.045 0.42 0.506 6.950 0.019 1.563Data from Rollinson (1993). * Eu3+/Eu2+ Italics are estimated

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Compatibility depends on minerals and melts involved. Compatibility depends on minerals and melts involved.

Which are incompatible? Why?Which are incompatible? Why?

Depends on the minerals involved!

Sr -> melt as ol & px separate -> plag (Ca) & not melt if plag is phenocryst phase

Commonly standardized to mantle compositions (olivine, pyroxenes, and perhaps garnet)

Thus the major elements Mg and Fe would usually be referred to as compatible, while K and Na as incompatible

For a For a rock,rock, determine the determine the bulk distribution bulk distribution coefficient Dcoefficient D for an element by calculating for an element by calculating the contribution for each mineralthe contribution for each mineral

eq. 9-4:eq. 9-4: DDii = = W WAA D Dii

WWAA = weight % of mineral A in the rock = weight % of mineral A in the rock

DDii = partition coefficient of element i in = partition coefficient of element i in

mineral Amineral A

AA

AA

Example: hypothetical garnet lherzolite = 60% olivine, 25% Example: hypothetical garnet lherzolite = 60% olivine, 25% orthopyroxene, 10% clinopyroxene, and 5% garnet (all by orthopyroxene, 10% clinopyroxene, and 5% garnet (all by weightweight), ), using the data in Table 9-1, is:using the data in Table 9-1, is:

DDErEr = (0.6 · 0.026) + (0.25 · 0.23) + (0.10 · 0.583) + (0.05 · 4.7) = = (0.6 · 0.026) + (0.25 · 0.23) + (0.10 · 0.583) + (0.05 · 4.7) =

0.3660.366




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Trace elements strongly partitioned into a single Trace elements strongly partitioned into a single mineralmineral

Ni - olivine in Table 9-1 = 14Ni - olivine in Table 9-1 = 14

Figure 9-1a.Figure 9-1a. Ni Harker Diagram for Crater Lake. From data compiled by Rick Conrey. From Ni Harker Diagram for Crater Lake. From data compiled by Rick Conrey. From Winter (2001) An Introduction to Igneous and Metamorphic Petrology. Prentice Hall.Winter (2001) An Introduction to Igneous and Metamorphic Petrology. Prentice Hall.

Incompatible trace elements concentrate Incompatible trace elements concentrate liquid liquid

Reflect the proportion of liquid at a given state of Reflect the proportion of liquid at a given state of crystallization or meltingcrystallization or melting

Figure 9-1b.Figure 9-1b. Zr Harker Diagram for Crater Lake. From data compiled by Rick Conrey. Zr Harker Diagram for Crater Lake. From data compiled by Rick Conrey. From Winter (2001) An Introduction to Igneous and Metamorphic Petrology. Prentice Hall.From Winter (2001) An Introduction to Igneous and Metamorphic Petrology. Prentice Hall.

Trace Element BehaviorTrace Element Behavior The concentration of a The concentration of a majormajor element in a element in a

phase is usually buffered by the system, so phase is usually buffered by the system, so that it varies little in a phase as the system that it varies little in a phase as the system composition changescomposition changes

At a given T we could vary At a given T we could vary XXmeltmelt from 20 from 20 60 % 60 % Mg/Fe without changing the Mg/Fe without changing the composition of the melt or composition of the melt or the olivinethe olivine

Trace elementTrace element concentrations are in the concentrations are in the Henry’s Law region of concentration, so Henry’s Law region of concentration, so their activity varies in direct relation to their their activity varies in direct relation to their concentration in the systemconcentration in the system

Trace element concentrations are in the Trace element concentrations are in the Henry’s Law region of concentration, so Henry’s Law region of concentration, so their activity varies in direct relation to their their activity varies in direct relation to their concentration in the systemconcentration in the system

Thus if XThus if XNiNi in the system doubles the X in the system doubles the XNiNi in all in all

phases will doublephases will double

Trace element concentrations are in the Trace element concentrations are in the Henry’s Law region of concentration, so Henry’s Law region of concentration, so their activity varies in direct relation to their their activity varies in direct relation to their concentration in the systemconcentration in the system

Thus if XThus if XNiNi in the system doubles the X in the system doubles the XNiNi in all in all

phases will doublephases will double

Because of this, the Because of this, the ratiosratios of trace elements of trace elements are often superior to the concentration of a are often superior to the concentration of a single element in identifying the role of a single element in identifying the role of a specific mineralspecific mineral

K/RbK/Rb often used often used the importance of the importance of amphiboleamphibole in a source rock in a source rock K & Rb behave very similarly, so K & Rb behave very similarly, so K/Rb should be ~ constantK/Rb should be ~ constant If amphibole, almost all K and Rb reside in itIf amphibole, almost all K and Rb reside in it Amphibole has a D of about 1.0 for K and 0.3 for RbAmphibole has a D of about 1.0 for K and 0.3 for Rb




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Sr and Ba (also Sr and Ba (also incompatibleincompatible elements) elements) SrSr is excluded from most common minerals is excluded from most common minerals

except except plagioclaseplagioclase BaBa similarly excluded except in similarly excluded except in alkali feldsparalkali feldspar




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CompatibleCompatible example: example: NiNi strongly fractionated strongly fractionated olivineolivine > pyroxene > pyroxene CrCr and and ScSc pyroxenespyroxenes » olivine » olivine Ni/Cr or Ni/Sc can distinguish the effects of olivine Ni/Cr or Ni/Sc can distinguish the effects of olivine

and augite in a partial melt or a suite of rocks and augite in a partial melt or a suite of rocks produced by fractional crystallizationproduced by fractional crystallization

Models of Magma EvolutionModels of Magma Evolution Batch MeltingBatch Melting

The melt remains resident until at some point it is The melt remains resident until at some point it is released and moves upwardreleased and moves upward

Equilibrium melting process with variable % Equilibrium melting process with variable % meltingmelting

Models of Magma EvolutionModels of Magma Evolution Batch MeltingBatch Melting

eq. 9-5eq. 9-5

CCLL = trace element concentration in the liquid = trace element concentration in the liquid

CCOO = trace element concentration in the original rock = trace element concentration in the original rock

before melting beganbefore melting began

F = wt fraction of melt F = wt fraction of melt producedproduced = melt/(melt + rock) = melt/(melt + rock)

CCCC

11DDii(1(1 F)F) FF

LL

OO

Batch MeltingBatch Melting

A plot of CA plot of CLL/C/COO vs. F for various vs. F for various

values of Dvalues of Dii using eq. 9-5 using eq. 9-5

DDii = 1.0 = 1.0

Figure 9-2.Figure 9-2. Variation in the relative concentration of a Variation in the relative concentration of a trace element in a liquid vs. source rock as a fiunction trace element in a liquid vs. source rock as a fiunction of D and the fraction melted, using equation (9-5) for of D and the fraction melted, using equation (9-5) for equilibrium batch melting. From Winter (2001) An equilibrium batch melting. From Winter (2001) An Introduction to Igneous and Metamorphic Petrology. Introduction to Igneous and Metamorphic Petrology. Prentice Hall.Prentice Hall.

DDii » 1.0 ( » 1.0 (compatible compatible element)element)

Very low concentration in Very low concentration in meltmelt

Especially for low % Especially for low % melting (low F)melting (low F)


Highly Highly incompatibleincompatible elements elements Greatly concentrated in Greatly concentrated in

the initial small fraction the initial small fraction of melt produced by of melt produced by partial meltingpartial melting

Subsequently diluted as Subsequently diluted as F increasesF increases


As F As F 1 the concentration of 1 the concentration of everyevery trace element in the trace element in the liquid = the source rock (Cliquid = the source rock (CLL/C/COO

1) 1)

As F As F 1 1

CCLL/C/COO

1 1

CC

1Di (1 F) F

L

O


As F As F 0 0 CCLL/C/COO 1/D 1/Dii

If we know CIf we know CLL of a magma derived of a magma derived

by a small degree of batch melting, by a small degree of batch melting, and we know Dand we know Dii we can estimate we can estimate

the concentration of that element the concentration of that element in the source region (Cin the source region (COO))

CC

1Di (1 F) F

L

O


For very For very incompatibleincompatible elements as D elements as Dii 0 0

equation 9-5 equation 9-5 reduces reduces to:to:

eq. 9-7eq. 9-7

C

C

1

FL

O

CC

1Di (1 F) F

L

O

If we know the concentration of a very If we know the concentration of a very incompatible element in both a magma and the incompatible element in both a magma and the source rock, we can determine the fraction of source rock, we can determine the fraction of partial melt producedpartial melt produced

Worked Example of Batch Melting: Worked Example of Batch Melting: Rb and Rb and SrSrBasalt with the mode:Basalt with the mode:

1.1. Convert to Convert to weightweight % minerals (W % minerals (Wolol W Wcpxcpx etc.) etc.)

Table 9-2. Conversion from mode to

weight percent

Mineral Mode Density Wt prop Wt%

ol 15 3.6 54 0.18

cpx 33 3.4 112.2 0.37

plag 51 2.7 137.7 0.45

Sum 303.9 1.00

Worked Example of Batch Melting: Worked Example of Batch Melting: Rb and Rb and SrSr

Table 9-2. Conversion from mode to

weight percent

Mineral Mode Density Wt prop Wt%

ol 15 3.6 54 0.18

cpx 33 3.4 112.2 0.37

plag 51 2.7 137.7 0.45

Sum 303.9 1.00

Basalt with the mode:Basalt with the mode:

1.1. Convert to Convert to weightweight % minerals (W % minerals (Wolol W Wcpxcpx etc.) etc.)

2.2. Use equation eq. 9-4: Use equation eq. 9-4: DDii = = W WAA D Dii

and the table of D values for Rb and Sr in each mineral and the table of D values for Rb and Sr in each mineral to calculate the bulk distribution coefficients: Dto calculate the bulk distribution coefficients: DRbRb = =

0.045 and D0.045 and DSrSr = 0.848 = 0.848

Table 9-3 . Batch Fractionation Model for Rb and Sr

CL/CO = 1/(D(1-F)+F)

DRb DSr

F 0.045 0.848 Rb/Sr0.05 9.35 1.14 8.190.1 6.49 1.13 5.730.15 4.98 1.12 4.430.2 4.03 1.12 3.610.3 2.92 1.10 2.660.4 2.29 1.08 2.110.5 1.89 1.07 1.760.6 1.60 1.05 1.520.7 1.39 1.04 1.340.8 1.23 1.03 1.200.9 1.10 1.01 1.09

3.3. Use the batch melting equation Use the batch melting equation

(9-5)(9-5) to calculate Cto calculate CLL/C/COO for various values of F for various values of F

From Winter (2001) An Introduction to Igneous and Metamorphic Petrology. Prentice Hall.From Winter (2001) An Introduction to Igneous and Metamorphic Petrology. Prentice Hall.

4.4. Plot C Plot CLL/C/COO vs. F for each element vs. F for each element

Figure 9-3.Figure 9-3. Change in the concentration Change in the concentration of Rb and Sr in the melt derived by of Rb and Sr in the melt derived by progressive batch melting of a basaltic progressive batch melting of a basaltic rock consisting of plagioclase, augite, rock consisting of plagioclase, augite, and olivine. From Winter (2001) An and olivine. From Winter (2001) An Introduction to Igneous and Introduction to Igneous and Metamorphic Petrology. Prentice Hall.Metamorphic Petrology. Prentice Hall.

Incremental Batch MeltingIncremental Batch Melting

Calculate batch melting for successive Calculate batch melting for successive batches (same equation)batches (same equation)

Must recalculate DMust recalculate Dii as solids change as as solids change as

minerals are minerals are selectivelyselectively melted (computer) melted (computer)

Fractional CrystallizationFractional Crystallization1. Crystals remain in equilibrium with each 1. Crystals remain in equilibrium with each

melt incrementmelt increment

Rayleigh fractionationRayleigh fractionation The other extreme: separation of each The other extreme: separation of each

crystal as it formed = perfectly continuous crystal as it formed = perfectly continuous fractional crystallization in a magma fractional crystallization in a magma chamberchamber

Rayleigh fractionationRayleigh fractionation

The other extreme: separation of each The other extreme: separation of each crystal as it formed = perfectly continuous crystal as it formed = perfectly continuous fractional crystallization in a magma fractional crystallization in a magma chamber chamber Concentration of some element in the Concentration of some element in the residualresidual

liquid, Cliquid, CLL is modeled by the Rayleigh equation: is modeled by the Rayleigh equation:

eq. 9-8eq. 9-8 CCLL/C/COO = F = F (D -1)(D -1) Rayleigh FractionationRayleigh Fractionation

Other models are used to analyzeOther models are used to analyze Mixing of magmasMixing of magmas Wall-rock assimilationWall-rock assimilation Zone refiningZone refining Combinations of processes Combinations of processes

Rare Earth Elements (REE)Rare Earth Elements (REE)

Membros do Grupo IIIA da tabela Periodica Membros do Grupo IIIA da tabela Periodica La -> to Lutetium (Z = 57 La -> to Lutetium (Z = 57 71) 71)

Todos tem similar propriedades Todos tem similar propriedades quimicas e fisicas -> comporta-se como uma quimicas e fisicas -> comporta-se como uma

serie coerente serie coerente Todos tem um estado de oxidação de 3+Todos tem um estado de oxidação de 3+

O raio Ionico diminui constantemente com O raio Ionico diminui constantemente com aumento do número atõmico (aumento do número atõmico (lanthanide lanthanide

contractioncontraction))

Existe contrastes e similaridades nos valores de D :Existe contrastes e similaridades nos valores de D :

Todos são incompativeisTodos são incompativeisTable 9-1. Partition Coefficients for some commonly used

trace elements in basaltic and andesitic rocks Bulk D calculation

Olivine Opx Cpx Garnet Plag Amph

Rb 0.006 0.02 0.04 0.001 0.1 0.3

Sr 0.01 0.01 0.14 0.001 1.8 0.57

Ba 0.006 0.12 0.07 0.002 0.23 0.31

Ni 14 5 2.6 0.4 0.01 3

Cr 2.1 10 8.4 0.17 10 1.6

La 0.007 0.02 0.08 0.05 0.14 0.27

Ce 0.009 0.02 0.34 0.05 0.14 0.34

Nd 0.009 0.05 0.6 0.07 0.08 0.19

Sm 0.009 0.05 0.9 0.06 0.08 0.91

Eu 0.008 0.05 0.9 0.9 0.1/1.5* 1.01

Tb 0.01 0.05 1 5.6 0.03 1.4

Er 0.013 0.31 1 18 0.08 0.48

Yb 0.014 0.34 0.2 30 0.07 0.97

Lu 0.016 0.11 0.82 35 0.08 0.89

data from Henderson (1982) * Eu3+/Eu2+ Italics are estimated

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Também Note:Também Note:

HREEHREE são menos são menos incompativeisincompativeis

Especialmente Especialmente em em granadagranada

EuEu tem tem 2+ 2+ concentra em concentra em plagioclasioplagioclasio

Diagramas ETR (REE)Diagramas ETR (REE)Plota-se a concentração no eixo-y- contra o Plota-se a concentração no eixo-y- contra o

aumento do numero atômico aumento do numero atômico

O grau deO grau de compatibilidade aumenta da esquerda compatibilidade aumenta da esquerda para direita no diagramapara direita no diagrama

Con

cent

rati

onC

once

ntra

tion

La Ce Nd Sm Eu Tb Er Dy Yb LuLa Ce Nd Sm Eu Tb Er Dy Yb Lu

-3

-2

-1

0

1

2

3

4

5

6

7

8

9

10

11

0 10 20 30 40 50 60 70 80 90 100

Atomic Number (Z)

Lo

g (

Ab

un

da

nce

in

CI

Ch

on

dri

tic

Me

teo

rite

) HHe

Li

Be

B

C

N

O

F

Sc

Fe

Ni

Ne MgSi

SCa

Ar

Ti

PbPtSn Ba

VK

NaAlP

Cl

ThU

Normaliza pelo meteorito condrito para eliminar o Normaliza pelo meteorito condrito para eliminar o efeito Oddo-Harkins efeito Oddo-Harkins e faz a escala do eixo-y mais e faz a escala do eixo-y mais funcional normalizando pelo padrãofuncional normalizando pelo padrão

Como se parece um diagrama de REE com a Como se parece um diagrama de REE com a analise do meteorito condrito?analise do meteorito condrito?

0.00

2.00

4.00

6.00

8.00

10.00

56 58 60 62 64 66 68 70 72

sam

ple

/ch

on

dri

te

L La Ce Nd Sm Eu Tb Er Yb Lu

?

Estimativa do comportamento do REE do manto Estimativa do comportamento do REE do manto primordialprimordial

Divide cada Divide cada elemento elemento

analisado pela analisado pela concentração concentração

no padrão no padrão condritocondrito

Diagramas de REE usando o modelo de fusão Diagramas de REE usando o modelo de fusão parcial de um granada lherzolito para diferentes parcial de um granada lherzolito para diferentes valores de F:valores de F:

Figure 9-4.Figure 9-4. Rare Earth Rare Earth concentrations (normalized to concentrations (normalized to chondrite) for melts produced at chondrite) for melts produced at various values of F via melting of a various values of F via melting of a hypothetical garnet lherzolite using hypothetical garnet lherzolite using the batch melting model (equation the batch melting model (equation 9-5). From Winter (2001) An 9-5). From Winter (2001) An Introduction to Igneous and Introduction to Igneous and Metamorphic Petrology. Prentice Metamorphic Petrology. Prentice Hall.Hall.

Calculado o D(La) para um lherzolito e Calculado o D(La) para um lherzolito e considerando um modelo com ponto de fusão de F = considerando um modelo com ponto de fusão de F =

0.1 -0.1 -LREE são menos compativeis do que HREE, então o LREE são menos compativeis do que HREE, então o

fundido se enriqufundido se enriquece emece em LREE -> (-) inclinação LREE -> (-) inclinaçãoA inclinação é maiorA inclinação é maior para menores valors de para menores valors de F F

(baixa % de fusão parcial)(baixa % de fusão parcial)Quando Quando F F 1 inclinação 1 inclinação 0 0 emem S/C = 1.0 d S/C = 1.0 desde esde

que todo manto foi fundido que todo manto foi fundido Note também o uso das RANote também o uso das RAZÕESZÕES para -> inclinação para -> inclinação

nos nos REE REE La/Lu razão -> inLa/Lu razão -> inclinaçãoclinação REE REE

Tb/Lu Tb/Lu parapara HREE somente (granada) HREE somente (granada)La/Sm -> LREE somenteLa/Sm -> LREE somente

Anomalia de Europio =Anomalia de Europio = quando o quando o plagioclasio:plagioclasio:

fenocristais fractionandofenocristais fractionando Como um solido residual na fonteComo um solido residual na fonte

Figure 9-5.Figure 9-5. REE diagram for 10% REE diagram for 10% batch melting of a hypothetical batch melting of a hypothetical lherzolite with 20% plagioclase, lherzolite with 20% plagioclase, resulting in a pronounced negative resulting in a pronounced negative Europium anomaly. From Winter Europium anomaly. From Winter (2001) An Introduction to Igneous (2001) An Introduction to Igneous and Metamorphic Petrology. and Metamorphic Petrology. Prentice Hall.Prentice Hall.

Eu* é o valor de Eu Eu* é o valor de Eu “deve” ter se estiver na “deve” ter se estiver na

forma de Euforma de Eu+2+2 -> -> plagioclasio plagioclasio

Eu sozinho é inconclusivo (baixo REE de baixo Eu)

Sm/Eu dedfine a a inclinação e a anomalia

Spider DiagramsSpider DiagramsUma extensão da técnica de normalização de Uma extensão da técnica de normalização de REE para um amplo espectro de elementosREE para um amplo espectro de elementos

Fig. 9-6. Spider diagram for an alkaline basalt from Gough Island, southern Atlantic. After Sun and MacDonough (1989). In A. D. Saunders and M. J. Norry (eds.), Magmatism in the Ocean Basins. Geol. Soc. London Spec. Publ., 42. pp. 313-345.

Spider diagaramas Spider diagaramas normalizados pelo condrito normalizados pelo condrito são comumente organizados são comumente organizados com aumento da com aumento da incompatibilidade esqquerda incompatibilidade esqquerda direita direitaFusão parcial do mantoFusão parcial do mantoDiferente estimativas Diferente estimativas diferente ordernaçãodiferente ordernação

Todos os Elementos são incompativeis (D<1) durante os processos de fusão parcial e cristalização fractionada. As principais excessões são:

Sr, que pode ser compativel se plagioclasio estiver envolvido ,

Y e Yb com granada

Ti com magnetita

Basaltos Oceanicos = grande grau de FP, seu spider diagramas pode refletir a fonte no padrões de elementos traço

Elementos menos incompatveis no lado direito podem ser menos enriquecidos durante a FP (particularmente os que sofrem pequenos graus de fusão), fazendo que a curva se incline para a esquerda-> (-)

MORB-normalized Spider MORB-normalized Spider Separa os LIL na esquerda e HFS na direita Separa os LIL na esquerda e HFS na direita Aumenta a incompatibilidade para o centro, coerente com o enriquecimento do magma

Figure 9-7.Figure 9-7. Ocean island basalt Ocean island basalt plotted on a mid-ocean ridge plotted on a mid-ocean ridge basalt (MORB) normalized basalt (MORB) normalized spider diagram of the type used spider diagram of the type used by Pearce (1983). Data from by Pearce (1983). Data from Sun and McDonough (1989). Sun and McDonough (1989). From Winter (2001) An From Winter (2001) An Introduction to Igneous and Introduction to Igneous and Metamorphic Petrology. Metamorphic Petrology. Prentice Hall.Prentice Hall.

Aplicação de Elementos Traço para sistema Igneos

Usar os elementos maiores em diagramas de variação, Usar os elementos maiores em diagramas de variação, para ver processos magmáticos em uma suite de rochas para ver processos magmáticos em uma suite de rochas

Grande variação para processos continuosGrande variação para processos continuos

Figure 9-1a.Figure 9-1a. Ni Harker Diagram for Ni Harker Diagram for Crater Lake. From data compiled by Crater Lake. From data compiled by Rick Conrey. From Winter (2001) An Rick Conrey. From Winter (2001) An Introduction to Igneous and Introduction to Igneous and Metamorphic Petrology. Prentice Metamorphic Petrology. Prentice Hall.Hall.

2. Identificaçao de rocha fonte com envolvimento de 2. Identificaçao de rocha fonte com envolvimento de um mineral em particular em processos de fusão um mineral em particular em processos de fusão parcial ou cristalização fracionadaparcial ou cristalização fracionada

Examplo: Pode usar os REE para distinguir entrre fonte de alta e baixa pressão de magmas derivados do manto

Na crosta continental profunda, e a profundidade de 100 km no manto, granada e clinopyroxenio são fases importantes, que permanecem como fases solida residual durante a geração de mais de 15-20% ded fusão parcial

Table 9-1. Partition Coefficients for some commonly used trace elements in basaltic and andesitic rocks Bulk D calculation

Olivine Opx Cpx Garnet Plag Amph

Rb 0.006 0.02 0.04 0.001 0.1 0.3

Sr 0.01 0.01 0.14 0.001 1.8 0.57

Ba 0.006 0.12 0.07 0.002 0.23 0.31

Ni 14 5 2.6 0.4 0.01 3

Cr 2.1 10 8.4 0.17 10 1.6

La 0.007 0.02 0.08 0.05 0.14 0.27

Ce 0.009 0.02 0.34 0.05 0.14 0.34

Nd 0.009 0.05 0.6 0.07 0.08 0.19

Sm 0.009 0.05 0.9 0.06 0.08 0.91

Eu 0.008 0.05 0.9 0.9 0.1/1.5* 1.01

Tb 0.01 0.05 1 5.6 0.03 1.4

Er 0.013 0.31 1 18 0.08 0.48

Yb 0.014 0.34 0.2 30 0.07 0.97

Lu 0.016 0.11 0.82 35 0.08 0.89

data from Henderson (1982) * Eu3+/Eu2+ Italics are estimated

Rare

Eart

h E

lem

ents

GarnetGarnet concentrates the HREE and fractionates among them concentrates the HREE and fractionates among them

Thus if garnet is in equilibrium with the partial melt (a residual Thus if garnet is in equilibrium with the partial melt (a residual phase in the source left behind) expect a steep (-) slope in REE phase in the source left behind) expect a steep (-) slope in REE and and HREEHREE

Shallow (< 40 Shallow (< 40 km) partial km) partial melting of the melting of the mantle will have mantle will have plagioclaseplagioclase in in the resuduum the resuduum and a Eu and a Eu anomaly will anomaly will resultresult

0.00

2.00

4.00

6.00

8.00

10.00

56 58 60 62 64 66 68 70 72

sa

mp

le/c

ho

nd

rite

La Ce Nd Sm Eu Tb Er Yb Lu

67% Ol 17% Opx 17% Cpx

0.00

2.00

4.00

6.00

8.00

10.00

56 58 60 62 64 66 68 70 72

sa

mp

le/c

ho

nd

rite


57% Ol 14% Opx 14% Cpx 14% Grt

Garnet and Plagioclase effect on HREE

0.00

2.00

4.00

6.00

8.00

10.00

sam

ple

/ch

on

dri

te

60% Ol 15% Opx 15% Cpx 10%Plag


Figure 9-3.Figure 9-3. Change in the concentration Change in the concentration of Rb and Sr in the melt derived by of Rb and Sr in the melt derived by progressive batch melting of a basaltic progressive batch melting of a basaltic rock consisting of plagioclase, augite, rock consisting of plagioclase, augite, and olivine. From Winter (2001) An and olivine. From Winter (2001) An Introduction to Igneous and Introduction to Igneous and Metamorphic Petrology. Prentice Hall.Metamorphic Petrology. Prentice Hall.

Table 9-6 A brief summary of some particularly useful trace elements in igneous petrology

Element Use as a petrogenetic indicator

Ni, Co, Cr Highly compatible elements. Ni (and Co) are concentrated in olivine, and Cr in spinel andclinopyroxene. High concentrations indicate a mantle source.

V, Ti Both show strong fractionation into Fe-Ti oxides (ilmenite or titanomagnetite). If they behavedifferently, Ti probably fractionates into an accessory phase, such as sphene or rutile.

Zr, Hf Very incompatible elements that do not substitute into major silicate phases (although they mayreplace Ti in sphene or rutile).

Ba, Rb Incompatible element that substitutes for K in K-feldspar, micas, or hornblende. Rb substitutesless readily in hornblende than K-spar and micas, such that the K/Ba ratio may distinguish thesephases.

Sr Substitutes for Ca in plagioclase (but not in pyroxene), and, to a lesser extent, for K in K-feldspar. Behaves as a compatible element at low pressure where plagioclase forms early, butas an incompatible at higher pressure where plagioclase is no longer stable.

REE Garnet accommodates the HREE more than the LREE, and orthopyroxene and hornblende doso to a lesser degree. Sphene and plagioclase accommodates more LREE. Eu2+

is stronglypartitioned into plagioclase.

Y Commonly incompatible (like HREE). Strongly partitioned into garnet and amphibole. Spheneand apatite also concentrate Y, so the presence of these as accessories could have asignificant effect.

Table 9-6.Table 9-6. After Green (1980). Tectonophys., After Green (1980). Tectonophys., 6363, , 367-385. From Winter (2001) An Introduction to 367-385. From Winter (2001) An Introduction to Igneous and Metamorphic Petrology. Prentice Hall.Igneous and Metamorphic Petrology. Prentice Hall.

Trace elements as a tool to Trace elements as a tool to determine paleotectonic determine paleotectonic

environmentenvironment Useful for rocks in mobile belts that are no Useful for rocks in mobile belts that are no

longer recognizably in their original settinglonger recognizably in their original setting Can trace elements be discriminators of Can trace elements be discriminators of

igneous environment?igneous environment? Approach is Approach is empiricalempirical on on modernmodern occurrences occurrences Concentrate on elements that are immobile Concentrate on elements that are immobile

during low/medium grade metamorphismduring low/medium grade metamorphism

Figure 9-8.Figure 9-8. (a)(a) after Pearce and Cann (1973), after Pearce and Cann (1973), Earth Planet, Sci. Lett., Earth Planet, Sci. Lett., 1919, 290-300, 290-300. . (b)(b) after Pearce (1982) after Pearce (1982) in in Thorpe (ed.), Andesites: Orogenic andesites and related rocks. Wiley. Chichester. pp. 525-548Thorpe (ed.), Andesites: Orogenic andesites and related rocks. Wiley. Chichester. pp. 525-548 , Coish et al. (1986), , Coish et al. (1986), Amer. J. Sci., Amer. J. Sci., 286286, 1-28, 1-28.. (c)(c) after Mullen (1983), after Mullen (1983), Earth Planet. Sci. Lett., Earth Planet. Sci. Lett., 6262, 53-62., 53-62.

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