7 FASES TERNARIAS

7/30/2019 7 FASES TERNARIAS

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C = 3: Ternary Systems:Example 1: Ternary Eutectic

Di - An - Fo

T

M

Anorthite

Forsterite

Diopside

Note three binary eutectics

No solid solution

Ternary eutectic = M


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T - X Projection of Di - An - Fo

Figure 7-2. Isobaric

diagram illustrating

the liquidus

temperatures in the

Di-An-Fo system at

atmospheric pressure(0.1 MPa). After

Bowen (1915), A. J.

Sci., and Morse

(1994), Basalts and

Phase Diagrams.

Krieger Publishers.


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Crystallization Relationships


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An + Liq

Liquid

Di + Liq

Di + An

a

An

Pure Fo formsJust as in binary

f = ?

F = ?


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f = 2 (Fo + Liq)

F = 3 - 2 + 1 = 2

If on liquidus, need to specify

only 2 intensive variables

to determine the system

T and or

and

X of pure Fo is fixed

XAnliq

XAnliq

XFoliq


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Lever principle relative proportions of liquid & Fo

At 1500oC

Liqx + Fo = bulka

x/Fo = a-Fo/x-a


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New continuous reaction as liquid follows cotectic:

LiqA LiqB + Fo + Di

Bulk solid extract Di/Fo in bulk solid extract using lever principle

1274

1392

Diopside

M

b

c

Fo + Liq

1387


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At 1300oC liquid = X

Imagine triangular plane X - Di - Fo balanced on bulk a

Liq/total solids = a-m/Liq-a

total Di/Fo = m-Fo/Di-m

a

Di

L iq x

Fom


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Partial Melting(remove melt):

i i


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Ternary Peritectic Systems:(at 0.1 MPa)


diagram illustrating

the cotectic and

peritectic curves in

the system forsterite-

anorthite-silica at 0.1

MPa. After Anderson

(1915) A. J. Sci., and

Irvine (1975) CIW

Yearb. 74.

3 binary systems:

Fo-An eutecticAn-SiO2 eutectic

Fo-SiO2 peritectic


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1890Fo En

a

b

y

x


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Works the same way as the Fo - En - SiO2 binary

ik

Fo En

1557


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Fo En

e b

f


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Diopside-Albite-Anorthite

Di - An Eutectic

Di - Ab Eutectic

Ab - An solid solution


diagram illustrating theliquidus temperatures

in the system diopside-

anorthite-albite at

atmospheric pressure

(0.1 MPa). After Morse

(1994), Basalts and

Phase Diagrams.Krieger Publushers

Figure 7-5 Isobaric


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Isobaric

polythermalprojection


diagram illustrating the

liquidus temperatures in

the system diopside-

anorthite-albite at

atmospheric pressure

(0.1 MPa). After Morse

(1994), Basalts andPhase Diagrams. Krieger

Publishers.


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Note:

Binary character is usually maintainedwhen a new component is added

Eutectic behavior remains eutectic

Peritectic behavior remains peritectic

Solid solutions remain so as well

Obli


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Oblique

ViewIsothermal

Section

Figure 7-8. Oblique view illustrating an isothermal section through the diopside-albite-anorthite

system. Figure 7-9. Isothermal section at 1250oC (and 0.1 MPa) in the system Di-An-Ab. Both fromMorse (1994), Basalts and Phase Diagrams. Krieger Publishers.

T F ld


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Ternary Feldspars

1118

Ab 20 40 60 80 An

1100

1200

1300

1400

1500

1557

T Co

PlagioclaseLiquid

Liquid

plus

Weight % An

Plagioclase

OrAb

Ab-rich feldspar

+ liquid

liquid

single feldspar

two feldspars

1200

1000

800TemperatureoC

Wt.%

a

cb

de

f

g h

i

jk

Figure 7-10. After Carmichael et al.(1974), Igneous Petrology. McGraw Hill.


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Ternary Feldspars

Trace of solvus

at three

temperature

intervals

Triangle shows coexisting

feldspars and liquid at

900oC

Figure 7-11. Winter (2001) An

Introduction to Igneous and

Metamorphic Petrology. PrenticeHall.


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4 - Component Diagrams

An

Figure 7-12. The system

diopside-anorthite-albite-forsterite. After

Yoder and Tilley (1962).

J. Petrol.


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> 4 Components

Figure 7-13. Pressure-temperature

phase diagram for the melting of a

Snake River (Idaho, USA) tholeiitic

basalt under anhydrous conditions.

After Thompson (1972). Carnegie

Inst. Wash Yb. 71


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olivine Calcic plagioclase

Mg pyroxene

Mg-Ca pyroxene

amphibole

biotite

(Spinel)

potash feldsparmuscovite

quartz

alkalic plagioclase

Calci-alkalic plagioclase

alkali-calcic plagioclase

Bowens Reaction Series

Discontinuous

Series

ContinuousSeries


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The Effect of Pressure

Liquid

Temperature

Solid

P1

P2

T1 T2


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Eutectic system

Figure 7-16. Effect of lithostatic pressure on the liquidus and eutectic composition in the diopside-anorthite system. 1 GPa data from Presnall et al. (1978). Contr. Min. Pet., 66, 203-220.

Th Eff t f W t M lti


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The Effect of Water on MeltingDry melting:solid liquid

Add water- water enters the meltReaction becomes:

solid + water = liq(aq)

Figure 7-19. The effect of H2O

saturation on the melting of albite,

from the experiments by Burnham

and Davis (1974). A J Sci 274, 902-

940. The dry melting curve is

from Boyd and England (1963).JGR 68, 311-323.


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Figure 7-20. Experimentally determined melting intervals of gabbro under H2O-free (dry), andH2O-saturated conditions. After Lambert and Wyllie (1972). J. Geol., 80, 693-708.

Dry and water saturated solidi for some common rock types


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Dry and water-saturated solidi for some common rock types

The more mafic the rock

the higher the melting

point

All solidi are greatly

lowered by water

Figure 7-21. H2O-saturated (solid)

and H2O-free (dashed) solidi

(beginning of melting) for

granodiorite (Robertson and Wyllie,

1971), gabbro (Lambert and Wyllie,

1972) and peridotite (H2O-saturated:

Kushiro et al., 1968; dry: Ito andKennedy, 1967).


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We know the behavior of water-free and water-saturated

melting by experiments, which are easy to control by

performing them in dry and wet sealed vessles

What about real rocks?

Some may be dry, some saturated, but most are morelikely to be in between these extremes

a fixed water content < saturation levels

a fixed water activity

Th Albit W t


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The Albite-Water

System

Red curves = melting for

a fixed mol % water in

the melt (Xw)

Blue curves tell the water

content of a water-

saturated melt

m

Figure 7-22. From Burnham and Davis(1974). A J Sci., 274, 902-940.


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Raise a melt with a ratio

of albite:water = 1:1

(Xwater= 0.5)

from point a at 925

o

C and1 GPa pressure, toward the

Earths surface under

isothermal conditions.

melt



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Conclusions:

A rising magma witha fixed % water will

progressively melt

At shallower levels it

will become saturated,

and expel water into

its surroundings



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Another example: isobaric

heating of albite with

10 mol % water at 0.6 GPa.


15% 20% 50% 100%


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Conclusion:

Although the addition of

water can drastically reduce

the melting point of rocks,the amount of melt produced

at the lower temperature may

be quite limited, depending

on the amount of wateravailable



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Melting of Albite with a

fixed activity of H2O

Fluid may be a CO2-H2O

mixture with Pf= PTotal



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Melting of Albite with a

fixed activity of H2O

Fluid may be a CO2-H2O

mixture with Pf= PTotal

Figure 7-26. From Millhollen et al. (1974). J. Geol., 82, 575-587.

Th l bilit f t i lt d d th t t f


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The solubility of water in a melt depends on the structure of

the melt (which reflects the structure of the mineralogical

equivalent)

Figure 7-25. The effect of H2O on the

diopside-anorthite liquidus. Dry and 1

atm from Figure 7-16, PH2O = Ptotal curve

for 1 GPa from Yoder (1965). CIW Yb 64.

Effect of Pressure Water and CO on the position


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Ne

Ab

Oversaturated(quartz-bearing)tholeiitic basalts

Highly undesaturated(nepheline-bearing)

alkali olivinebasalts

3GPa2GPa

1GPa

1atm

Volatile-free

Ne

Ab

Oversaturated(quartz-bearing)tholeiitic basalts

Highly undesaturated(nepheline-bearing)

alkali olivinebasalts

CO2

H2Odry

P = 2 GPa

Effect of Pressure, Water, and CO2 on the position

of the eutectic in the basalt system

Increased pressure moves the

ternary eutectic (first melt) fromsilica-saturated to highly undersat.

alkaline basalts

Water moves the (2 GPa) eutectic

toward higher silica, while CO2

moves it to more alkaline types

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7 FASES TERNARIAS