trace and reesfunnel.sfsu.edu/courses/geol480/lectures/trace-rees.pdf · 2005. 11. 4. · k/rb...
TRANSCRIPT
Trace ElementsTrace Elements
NoteNotemagnitudemagnitudeof of majormajorelementelementchangeschanges
Figure 8-2. Harker variation diagram for310 analyzed volcanic rocks from CraterLake (Mt. Mazama), Oregon Cascades.Data compiled by Rick Conrey (personalcommunication). From Winter (2001) AnFrom Winter (2001) AnIntroduction to Igneous and MetamorphicIntroduction to Igneous and MetamorphicPetrology. Prentice Hall.Petrology. Prentice Hall.
wt %
wt %
Figure 9-1.Figure 9-1. Harker Diagram for Crater Lake. From data Harker Diagram for Crater Lake. From datacompiled by Rick compiled by Rick ConreyConrey. From Winter (2001) An Introduction. From Winter (2001) An Introductionto Igneous and Metamorphic Petrology. Prentice Hall.to Igneous and Metamorphic Petrology. Prentice Hall.
NoteNotemagnitudemagnitudeof of tracetraceelementelementchangeschanges
Trace ElementsTrace Elements
ppm
ppm
ppm
ppm
Element DistributionElement DistributionGoldschmidtGoldschmidt’’s rules (simplistic, but useful)s rules (simplistic, but useful)
1.1. Two ions with the same valence and radiusTwo ions with the same valence and radiusshould exchange easily and enter a solidshould exchange easily and enter a solidsolution in amounts equal to their overallsolution in amounts equal to their overallproportionsproportions
How does Rb behave? Ni?How does Rb behave? Ni?
GoldschmidtGoldschmidt’’s ruless rules2. If two ions have a similar radius and the same2. If two ions have a similar radius and the same
valence: the smaller ion is preferentially incorporatedvalence: the smaller ion is preferentially incorporatedinto the solid over the liquidinto the solid over the liquid
Fig. 6-10. Isobaric T-X phasediagram at atmosphericpressure After Bowen andShairer (1932), Amer. J. Sci. 5thSer., 24, 177-213. From WinterFrom Winter(2001) An Introduction to(2001) An Introduction toIgneous and MetamorphicIgneous and MetamorphicPetrology. Prentice Hall.Petrology. Prentice Hall.
Relative ionic radii for common valencesand coordination numbers
Preference forPreference formineral phasemineral phase
PreferencePreferencefor meltfor melt
Plot of ionic radius vs. ionic charge fortrace elements of geological interest.Ionic radii are quoted for eight-foldcoordination to allow for comparisonbetween elements. From Rollinson(1993).
Ionic chargeIonic chargevs. radiusvs. radius
3. If two ions have a similar radius, but differentvalence: the ion with the higher charge ispreferentially incorporated into the solid over theliquid
Chemical FractionationChemical Fractionation
The uneven distribution of an ion betweenThe uneven distribution of an ion betweentwo competing (equilibrium) phasestwo competing (equilibrium) phases
Exchange equilibrium of a Exchange equilibrium of a componentcomponent ii betweenbetweentwo two phasesphases (solid and liquid) (solid and liquid)
ii (liquid)(liquid) = = ii (solid)(solid)
KKDD = = = =
K =K = equilibrium constantequilibrium constant
a a solidsolid
a a liquidliquidii
ii
γγ XX solidsolid
γγ XX liquidliquidii
ii
ii
ii
Trace element concentrations are in theTrace element concentrations are in theHenryHenry’’s Law region of concentration, sos Law region of concentration, sotheir activity varies in direct relation to theirtheir activity varies in direct relation to theirconcentration in the system, where [a] = (c)concentration in the system, where [a] = (c)
Thus if Thus if XXNiNi in the system doubles the in the system doubles the XXNiNi ininall all phases will doublephases will double This does not mean that This does not mean that XXNiNi in all phasesin all phases
is the same, since trace elements dois the same, since trace elements dofractionate. Rather the fractionate. Rather the XXNiNi within eachwithin eachphase will vary in proportion to thephase will vary in proportion to thesystem concentrationsystem concentration
incompatibleincompatible elements are concentrated in the elements are concentrated in themeltmelt
(K(KDD or D) or D) «« 1 1
compatiblecompatible elements are concentrated in the elements are concentrated in thesolidsolid
KKDD or D or D »» 1 1
where D is the partition coefficient for any given trace where D is the partition coefficient for any given trace element between phases; D is a constant for dilute element between phases; D is a constant for dilute concentrations of elementsconcentrations of elements
For dilute solutions can substitute D for KFor dilute solutions can substitute D for KDD::
D =D =
Where CWhere CSS = the concentration of some element in = the concentration of some element inthe solid phasethe solid phase
CCSSCCLL
IncompatibleIncompatible elements commonly elements commonly →→ two subgroups two subgroups
Smaller, highly charged Smaller, highly charged high field strength (HFS)high field strength (HFS)elementselements (REE, Th, U, Ce, Pb(REE, Th, U, Ce, Pb4+4+, Zr, Hf, Ti, Nb,, Zr, Hf, Ti, Nb,Ta)Ta)
Low field strength Low field strength large ion lithophile (LIL)large ion lithophile (LIL)elements elements (K, Rb, Cs, Ba, Pb(K, Rb, Cs, Ba, Pb2+2+, Sr, Eu, Sr, Eu2+2+)) are more are moremobile, particularly if a fluid phase is involvedmobile, particularly if a fluid phase is involved
High field strength (HFS) elementsHigh field strength (HFS) elementsSmaller, highly chargedSmaller, highly charged
Large Ion Large Ion Lithophiles Lithophiles ((LILsLILs))Low field strength (large ions, Low field strength (large ions, lower charge), more mobilelower charge), more mobile
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
Rar
e Ea
rth E
lem
ents
Compatibility depends on minerals and melts involved.Compatibility depends on minerals and melts involved.
Which are incompatible? Why?Which are incompatible? Why?
For a For a rock,rock, determine the determine the bulk distributionbulk distributioncoefficient Dcoefficient D for an element by calculating for an element by calculatingthe contribution for each mineralthe contribution for each mineral
DDii = = ΣΣ W WAA DDiAiA
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 = (0.6 ·· 0.026) + (0.25 0.026) + (0.25 ·· 0.23) + (0.10 0.23) + (0.10 ·· 0.583) + (0.05 0.583) + (0.05 ·· 4.7) = 4.7) = 0.3660.366
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
Rar
e Ea
rth E
lem
ents
Trace elements strongly partitioned into a single mineralTrace elements strongly partitioned into a single mineral Ni - olivine = 14Ni - olivine = 14
Figure 9-1a.Figure 9-1a. Ni Harker Diagram for Crater Lake. From data compiled by Rick Ni Harker Diagram for Crater Lake. From data compiled by Rick ConreyConrey. From. FromWinter (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 ofReflect the proportion of liquid at a given state ofcrystallization or meltingcrystallization or melting
Figure 9-1b.Figure 9-1b. Zr Harker Diagram for Crater Lake. From data compiled by Rick Zr Harker Diagram for Crater Lake. From data compiled by Rick ConreyConrey..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 phase is element in a phase is
usually buffered by the system, so that it variesusually buffered by the system, so that it varieslittle in a phase as the system composition changeslittle in a phase as the system composition changes
At a given T we could varyAt a given T we could varyXXmeltmelt from 20 from 20 →→ 60 % 60 %Mg/Fe without changing theMg/Fe without changing thecomposition of the melt orcomposition of the melt orthe olivinethe olivine
Trace elementTrace element concentrations are in theconcentrations are in theHenryHenry’’s Law region of concentration, sos Law region of concentration, sotheir activity varies in direct relation to theirtheir activity varies in direct relation to theirconcentration in the systemconcentration in the system
Trace element concentrations are in theTrace element concentrations are in theHenryHenry’’s Law region of concentration, sos Law region of concentration, sotheir activity varies in direct relation to theirtheir activity varies in direct relation to theirconcentration in the systemconcentration in the system
Thus if Thus if XXNiNi in the system doubles the in the system doubles the XXNiNi ininall phases will doubleall phases will double
Trace element concentrations are in theTrace element concentrations are in theHenryHenry’’s Law region of concentration, sos Law region of concentration, sotheir activity varies in direct relation to theirtheir activity varies in direct relation to theirconcentration in the systemconcentration in the system
Thus if Thus if XXNiNi in the system doubles the in the system doubles the XXNiNi ininall all phases will doublephases will double
Because of this, the Because of this, the ratiosratios of trace elements of trace elementsare often superior to the concentration of aare often superior to the concentration of asingle element in identifying the role of asingle element in identifying the role of aspecific 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
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
Rar
e Ea
rth E
lem
ents
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
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
Rar
e Ea
rth E
lem
ents
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 olivineNi/Cr or Ni/Sc can distinguish the effects of olivine
and augite in a partial melt or a suite of rocksand augite in a partial melt or a suite of rocksproduced by fractional crystallizationproduced by fractional crystallization
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
Rar
e Ea
rth E
lem
ents
Models of Magma EvolutionModels of Magma Evolution Batch MeltingBatch Melting
The melt remains resident until at some point it isThe melt remains resident until at some point it isreleased 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
CCLL = trace element concentration in the liquid = trace element concentration in the liquidCCOO = trace element concentration in the original rock = trace element concentration in the original rock
before melting beganbefore melting beganF = 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 the using theprevious equationprevious equation
DDii = 1.0 = 1.0
Figure 9-2.Figure 9-2. Variation in the relative concentration of a Variation in the relative concentration of atrace element in a liquid vs. source rock as a trace element in a liquid vs. source rock as a fiunctionfiunctionof D and the fraction melted, using equation (9-5) forof D and the fraction melted, using equation (9-5) forequilibrium batch melting. From Winter (2001) Anequilibrium batch melting. From Winter (2001) AnIntroduction 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 inVery low concentration inmeltmelt
Especially for low %Especially for low %melting (low F)melting (low F)
Figure 9-2.Figure 9-2. Variation in the relative concentration of a Variation in the relative concentration of atrace element in a liquid vs. source rock as a trace element in a liquid vs. source rock as a fiunctionfiunctionof D and the fraction melted, using equation (9-5) forof D and the fraction melted, using equation (9-5) forequilibrium batch melting. From Winter (2001) Anequilibrium batch melting. From Winter (2001) AnIntroduction to Igneous and Metamorphic Petrology.Introduction to Igneous and Metamorphic Petrology.Prentice Hall.Prentice Hall.
Highly Highly incompatibleincompatible elements elements•• Greatly concentrated in theGreatly concentrated in the
initial small fraction of meltinitial small fraction of meltproduced by partial meltingproduced by partial melting
•• Subsequently diluted as F Subsequently diluted as Fincreasesincreases
Figure 9-2.Figure 9-2. Variation in the relative concentration of a Variation in the relative concentration of atrace element in a liquid vs. source rock as a trace element in a liquid vs. source rock as a fiunctionfiunctionof D and the fraction melted, using equation (9-5) forof D and the fraction melted, using equation (9-5) forequilibrium batch melting. From Winter (2001) Anequilibrium batch melting. From Winter (2001) AnIntroduction to Igneous and Metamorphic Petrology.Introduction to Igneous and Metamorphic Petrology.Prentice Hall.Prentice Hall.
As F As F →→ 1 the concentration of 1 the concentration ofeveryevery trace element in the liquid trace element in the liquid= the source rock (C= the source rock (CLL/C/COO→→ 1) 1)
As F As F →→ 1 1CCLL/C/COO →→ 1 1
CC
1Di(1 F) F
L
O
=− +
Figure 9-2.Figure 9-2. Variation in the relative concentration of a Variation in the relative concentration of atrace element in a liquid vs. source rock as a trace element in a liquid vs. source rock as a fiunctionfiunctionof D and the fraction melted, using equation (9-5) forof D and the fraction melted, using equation (9-5) forequilibrium batch melting. From Winter (2001) Anequilibrium batch melting. From Winter (2001) AnIntroduction to Igneous and Metamorphic Petrology.Introduction to Igneous and Metamorphic Petrology.Prentice Hall.Prentice Hall.
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 derivedby 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 estimatethe concentration of that element inthe concentration of that element inthe source region (Cthe source region (COO))
CC
1Di(1 F) F
L
O
=− +
Figure 9-2.Figure 9-2. Variation in the relative concentration of a Variation in the relative concentration of atrace element in a liquid vs. source rock as a trace element in a liquid vs. source rock as a fiunctionfiunctionof D and the fraction melted, using equation (9-5) forof D and the fraction melted, using equation (9-5) forequilibrium batch melting. From Winter (2001) Anequilibrium batch melting. From Winter (2001) AnIntroduction to Igneous and Metamorphic Petrology.Introduction to Igneous and Metamorphic Petrology.Prentice Hall.Prentice Hall.
For very For very incompatibleincompatible elements as D elements as Dii →→ 0 0
reduces to:reduces to:
CC
1F
L
O
=
CC
1Di (1 F) F
L
O
=− +
If we know the concentration of a veryIf we know the concentration of a veryincompatible element in both a magma and theincompatible element in both a magma and thesource rock, we can determine the fraction ofsource rock, we can determine the fraction ofpartial melt producedpartial melt produced
Worked Example of Batch Melting: Worked Example of Batch Melting: Rb and SrRb and SrBasalt with the mode:Basalt with the mode:
1.1. Convert to Convert to weightweight % minerals ( % minerals (WWolol W Wcpxcpx etc.)etc.)
Table 9-2. Conversion from mode toweight percent
Mineral Mode Density Wt prop Wt%ol 15 3.6 54 0.18cpx 33 3.4 112.2 0.37plag 51 2.7 137.7 0.45
Sum 303.9 1.00
Worked Example of Batch Melting: Worked Example of Batch Melting: Rb and SrRb and Sr
Table 9-2. Conversion from mode toweight percent
Mineral Mode Density Wt prop Wt%ol 15 3.6 54 0.18cpx 33 3.4 112.2 0.37plag 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 ( % minerals (WWolol W Wcpxcpx etc.)etc.)
2.2. Use: Use: DDii = = ΣΣ W WAA D Dii
and the table of D values for Rb and Sr in each mineraland the table of D values for Rb and Sr in each mineralto calculate the bulk distribution coefficients: to calculate the bulk distribution coefficients: DDRbRb ==0.045 and 0.045 and DDSrSr = 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 to calculate C Use the batch melting equation to calculate CLL/C/COOfor various values of Ffor 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 concentrationof Rb and Sr in the melt derived byof Rb and Sr in the melt derived byprogressive batch melting of a basalticprogressive batch melting of a basalticrock consisting of plagioclase, augite,rock consisting of plagioclase, augite,and olivine. From Winter (2001) Anand olivine. From Winter (2001) AnIntroduction to Igneous andIntroduction to Igneous andMetamorphic Petrology. Prentice Hall.Metamorphic Petrology. Prentice Hall.
Incremental Batch MeltingIncremental Batch Melting
Calculate batch melting for successiveCalculate batch melting for successivebatches (same equation)batches (same equation)
Must recalculate DMust recalculate Dii as solids change as as solids change asminerals are minerals are selectivelyselectively melted (computer) melted (computer)
Fractional CrystallizationFractional Crystallization1. Crystals remain in equilibrium with each1. Crystals remain in equilibrium with each
melt incrementmelt increment
Rayleigh fractionationRayleigh fractionation The other extreme: separation of eachThe other extreme: separation of each
crystal as it formed = perfectly continuouscrystal as it formed = perfectly continuousfractional crystallization in a magmafractional crystallization in a magmachamberchamber
Rayleigh fractionationRayleigh fractionation The other extreme: separation of each The other extreme: separation of each
crystal as it formed = perfectly continuouscrystal as it formed = perfectly continuousfractional crystallization in a magmafractional crystallization in a magmachamberchamber Concentration of some element in the Concentration of some element in the residualresidual
liquid, Cliquid, CLL is modeled by the Rayleigh is modeled by the Rayleighequation:equation:
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 processesCombinations of processes
The Rare Earth Elements (REE)The Rare Earth Elements (REE)
Contrasts and similarities in the D values:Contrasts and similarities in the D values:All are incompatibleAll are incompatible
Table 9-1 . Partition Coefficients for some commonly used trace elements in basaltic and andesitic rocks Bulk D calculation
Olivine Opx Cpx Garnet Plag AmphRb 0.006 0.02 0.04 0.001 0.1 0.3Sr 0.01 0.01 0.14 0.001 1.8 0.57Ba 0.006 0.12 0.07 0.002 0.23 0.31Ni 14 5 2.6 0.4 0.01 3Cr 2.1 10 8.4 0.17 10 1.6La 0.007 0.02 0.08 0.05 0.14 0.27Ce 0.009 0.02 0.34 0.05 0.14 0.34Nd 0.009 0.05 0.6 0.07 0.08 0.19Sm 0.009 0.05 0.9 0.06 0.08 0.91Eu 0.008 0.05 0.9 0.9 0.1/1.5* 1.01Tb 0.01 0.05 1 5.6 0.03 1.4Er 0.013 0.31 1 18 0.08 0.48Yb 0.014 0.34 0.2 30 0.07 0.97Lu 0.016 0.11 0.82 35 0.08 0.89data from Henderson (1982) * Eu3+/Eu2+ Italics are estimated
Rar
e E
arth
Ele
men
ts
Also Note:Also Note:
HREEHREE are less are lessincompatibleincompatible
Especially in Especially ingarnetgarnet
EuEu can can →→ 2+ 2+which conc.which conc.in in plagioclaseplagioclase
REE DiagramsREE DiagramsPlots of concentration as the ordinate (y-axis)Plots of concentration as the ordinate (y-axis)
against increasing atomic numberagainst increasing atomic number Degree of compatibility increases from leftDegree of compatibility increases from left
to right across the diagramto right across the diagram
Con
cent
ratio
nC
once
ntra
tion
La Ce Nd Sm Eu Tb ErLa Ce Nd Sm Eu Tb Er Dy Dy Yb LuYb 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)
Log
(Abu
ndan
ce in
CI C
hond
ritic
Met
eorit
e)
HHe
Li
Be
B
C
N
O
FSc
FeNi
Ne MgSiS
CaAr
Ti
PbPtSn BaV
K
NaAlPCl
ThU
Eliminate Eliminate Oddo-Harkins effectOddo-Harkins effect and make y-scale and make y-scalemore functional by normalizing to a standardmore functional by normalizing to a standard estimates of primordial mantle REEestimates of primordial mantle REE chondrite meteorite concentrationschondrite meteorite concentrations
What would an REE diagram lookWhat would an REE diagram looklike for an analysis of a chondritelike for an analysis of a chondrite
meteorite?meteorite?
0.00
2.00
4.00
6.00
8.00
10.00
56 58 60 62 64 66 68 70 72
sam
ple/
chon
drite
L La Ce Nd Sm Eu Tb Er Yb Lu
?
Divide each element in analysis by theDivide each element in analysis by theconcentration in a chondrite standardconcentration in a chondrite standard
0.00
2.00
4.00
6.00
8.00
10.00
56 58 60 62 64 66 68 70 72
sam
ple/
chon
drite
L La Ce Nd Sm Eu Tb Er Yb Lu
REE diagrams using batch melting model ofREE diagrams using batch melting model ofa garnet lherzolite for various values of F:a garnet lherzolite for various values of F:
Figure 9-4.Figure 9-4. Rare Earth Rare Earthconcentrations (normalized toconcentrations (normalized tochondrite) for melts produced atchondrite) for melts produced atvarious values of F via melting of avarious values of F via melting of ahypothetical garnet lherzolite usinghypothetical garnet lherzolite usingthe batch melting model (equationthe batch melting model (equation9-5). From Winter (2001) An9-5). From Winter (2001) AnIntroduction to Igneous andIntroduction to Igneous andMetamorphic Petrology. PrenticeMetamorphic Petrology. PrenticeHall.Hall.
Europium anomalyEuropium anomaly when plagioclase is when plagioclase is a fractionating phenocrysta fractionating phenocryst
oror a residual solid in sourcea residual solid in source
Figure 9-5.Figure 9-5. REE diagram for 10% REE diagram for 10%batch melting of a hypotheticalbatch melting of a hypotheticallherzolite with 20% plagioclase,lherzolite with 20% plagioclase,resulting in a pronounced negativeresulting in a pronounced negativeEuropium anomaly. From WinterEuropium anomaly. From Winter(2001) An Introduction to Igneous(2001) An Introduction to Igneousand Metamorphic Petrology.and Metamorphic Petrology.Prentice Hall.Prentice Hall.
Spider DiagramsSpider DiagramsAn extension of the normalized REEAn extension of the normalized REEtechnique to a broader spectrum of elementstechnique to a broader spectrum of elements
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.
Chondrite-normalized spiderChondrite-normalized spiderdiagrams are commonlydiagrams are commonlyorganized by (the authororganized by (the author’’ssestimate) of increasingestimate) of increasingincompatibility L incompatibility L ←← R R
Different estimates Different estimates →→different ordering (poordifferent ordering (poorstandardization)standardization)
MORB-normalized SpiderMORB-normalized SpiderSeparates LIL and HFSSeparates LIL and HFS
Figure 9-7.Figure 9-7. Ocean island basalt Ocean island basaltplotted on a mid-ocean ridgeplotted on a mid-ocean ridgebasalt (MORB) normalizedbasalt (MORB) normalizedspider diagram of the type usedspider diagram of the type usedby Pearce (1983). Data fromby Pearce (1983). Data fromSun and McDonough (1989).Sun and McDonough (1989).From Winter (2001) AnFrom Winter (2001) AnIntroduction to Igneous andIntroduction to Igneous andMetamorphic Petrology.Metamorphic Petrology.Prentice Hall.Prentice Hall.
Application of Trace Elements toIgneous Systems
1. Use like major elements on variation diagrams to1. Use like major elements on variation diagrams todocument FX, assimilation, etc. in a suite of rocksdocument FX, assimilation, etc. in a suite of rocks More sensitive More sensitive →→ larger variations as process larger variations as process
continuescontinues
Figure 9-1a.Figure 9-1a. Ni Harker Diagram for Ni Harker Diagram forCrater Lake. From data compiled byCrater Lake. From data compiled byRick Rick ConreyConrey. From Winter (2001) An. From Winter (2001) AnIntroduction to Igneous andIntroduction to Igneous andMetamorphic Petrology. Prentice Hall.Metamorphic Petrology. Prentice Hall.
2. Identification of the source rock or a particular2. Identification of the source rock or a particularmineral involved in either partial melting ormineral involved in either partial melting orfractional crystallization processesfractional crystallization processes
Table 9-1 . Partition Coefficients for some commonly used trace elements in basaltic and andesitic rocks Bulk D calculation
Olivine Opx Cpx Garnet Plag AmphRb 0.006 0.02 0.04 0.001 0.1 0.3Sr 0.01 0.01 0.14 0.001 1.8 0.57Ba 0.006 0.12 0.07 0.002 0.23 0.31Ni 14 5 2.6 0.4 0.01 3Cr 2.1 10 8.4 0.17 10 1.6La 0.007 0.02 0.08 0.05 0.14 0.27Ce 0.009 0.02 0.34 0.05 0.14 0.34Nd 0.009 0.05 0.6 0.07 0.08 0.19Sm 0.009 0.05 0.9 0.06 0.08 0.91Eu 0.008 0.05 0.9 0.9 0.1/1.5* 1.01Tb 0.01 0.05 1 5.6 0.03 1.4Er 0.013 0.31 1 18 0.08 0.48Yb 0.014 0.34 0.2 30 0.07 0.97Lu 0.016 0.11 0.82 35 0.08 0.89data from Henderson (1982) * Eu3+/Eu2+ Italics are estimated
Rar
e E
arth
Ele
men
ts
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 residualThus if garnet is in equilibrium with the partial melt (a residualphase in the source left behind) expect a steep (-) slope in REE phase in the source left behind) expect a steep (-) slope in REE andandHREEHREE
Shallow (< 40Shallow (< 40km) partialkm) partialmelting of themelting of themantle will havemantle will haveplagioclaseplagioclase in inthe the resuduumresuduumand a Euand a Euanomaly willanomaly willresultresult
0.00
2.00
4.00
6.00
8.00
10.00
56 58 60 62 64 66 68 70 72
sam
ple/
chon
drite
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
sam
ple/
chon
drite
La Ce Nd Sm Eu Tb Er Yb Lu
57% Ol 14% Opx 14% Cpx 14% Grt
Garnet and Plagioclaseeffect on HREE
0.00
2.00
4.00
6.00
8.00
10.00
sam
ple/
chon
drite
60% Ol 15% Opx 15% Cpx 10%Plag
La Ce Nd Sm Eu Tb Er Yb Lu
Figure 9-3.Figure 9-3. Change in the concentration Change in the concentrationof Rb and Sr in the melt derived byof Rb and Sr in the melt derived byprogressive batch melting of a basalticprogressive batch melting of a basalticrock consisting of plagioclase, augite,rock consisting of plagioclase, augite,and olivine. From Winter (2001) Anand olivine. From Winter (2001) AnIntroduction to Igneous andIntroduction to Igneous andMetamorphic 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). After Green (1980). TectonophysTectonophys., ., 6363, 367-385. From Winter (2001) An Introduction to Igneous and, 367-385. From Winter (2001) An Introduction to Igneous andMetamorphic Petrology. Prentice Hall.Metamorphic Petrology. Prentice Hall.
Trace elements as a tool toTrace elements as a tool todetermine determine paleotectonicpaleotectonic
environmentenvironment Useful for rocks in mobile belts that are noUseful for rocks in mobile belts that are no
longer recognizably in their original settinglonger recognizably in their original setting Can trace elements be discriminators ofCan trace elements be discriminators of
igneous environment?igneous environment? Approach is Approach is empiricalempirical on on modernmodern occurrences occurrences Concentrate on elements that are immobileConcentrate 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 after Pearce and Cann Cann (1973), (1973), Earth Planet, Sci. Earth Planet, Sci. LettLett., ., 1919, 290-300, 290-300. . (b)(b) after Pearce (1982) after Pearce (1982) in Thorpe (ed.),in Thorpe (ed.),Andesites: Orogenic andesites and related rocks. Wiley. Andesites: Orogenic andesites and related rocks. Wiley. ChichesterChichester. pp. 525-548. pp. 525-548, , Coish Coish et al. (1986), 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. Earth Planet. Sci. LettLett., ., 6262, 53-62., 53-62.