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Chapter 6- Phase Relations and Binary Systems

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Phase Diagrams 1557 s u d i u q i L 1500 Liquid 1600 a Plagioclase 1400 1553 Liquid Liquidus o T C 1500 b c plus T C o 1300 Liquid 1400 Anorthite + Liquid 1392 ... – PowerPoint PPT presentation

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Title: Chapter 6- Phase Relations and Binary Systems


1
Phase Diagrams
2
Updates/questions
  • Lab Field trip on Saturday 18th, waivers in lab
  • Topics phase diagrams (today and Wednesday)
  • Phase rule
  • 1 component systems
  • 2 component systems
  • Eutectic
  • Solid solution
  • Solvus

3
The Phase Rule
F C - f 2
4
The Phase Rule
F C - f 2
5
The Phase Rule
F C - f 2
6
The Phase Rule
F C - f 2
7
1 - Component Systems
A
B
After Swamy and Saxena (1994), J. Geophys. Res.,
99, 11,787-11,794. AGU
8
1 - C Systems
Temperature oC
After Bridgman (1911, Proc. Amer. Acad. Arts and
Sci., 5, 441-513 1936, J. Chem. Phys., 3,
597-605 1937, J. Chem. Phys., 5, 964-966.
9
Binary Systems
1600
1553
Liquid
Liquidus
1500
T
C
o
1400
Anorthite Liquid
1392
Diopside Liquid
1300
1274
1200
Diopside Anorthite
Di
20
40
60
80
An
Wt. Anorthite
Isobaric T-X phase diagram at atmospheric
pressure (After Bowen (1915), Amer. J. Sci. 40,
161-185.
10
Crystallization in Binary Systems
11
Crystallization first crystals
12
Crystallization ongoing
13
Crystallization eutectic
1600
a
1553
Liquid
Liquidus
1500
b
c
T
C
o
1400
Anorthite Liquid
1392
d
Diopside Liquid
1300
g
h
1274
1200
Diopside Anorthite
Di
20
40
60
80
An
Wt. Anorthite
14
Crystallization levers
The lever principle fraction of melt vs.
crystals
d
f
e
D
Amount of liquid
ef

de
ef
Amount of solid
An
de
15
Crystallization left half
16
Augite forms before plagioclase
Gabbro of the Stillwater Complex, Montana
This forms on the left side of the eutectic
17
Plagioclase forms before augite
Ophitic texture
Diabase dike
This forms on the right side of the eutectic
18
Additional notes
19
Fractional crystallization
20
Equilibrium melting
21
Solid solutions
Isobaric T-X phase diagram at atmospheric
pressure (after Bowen 1913, Amer. J. Sci., 35,
577-599).
22
Feldspar composition
23
Solid solutions phase rule
24
Crystallization
a
1557
1500
b
c
Liquid
Plagioclase
1400
o
T C

1300
Liquid
Plagioclase
1200
1118
1100
Ab
20
40
60
An
80
25
Crystallization phase rule
F 2 - 2 1 1 (univariant) Must specify
only one variable from among T
a
1557
1500
b
c
Liquid
Plagioclase
1400
o
T C

and are dependent upon T The
slope of the solidus and liquidus are the
expressions of this relationship
1300
Liquid
Plagioclase
1200
1118
1100
Ab
20
40
60
An
80
26
Ongoing crystallization
a
1557
1500
b
c
Liquid
f
d
Plagioclase
1400
o
T C

1300
Liquid
Plagioclase
1200
1118
1100
Ab
20
40
60
An
80
27
The lever principle
Amount of liquid
ef

Amount of solid
de
where d the liquid composition, f the solid
composition and e the bulk composition
a
b
c
Liquid
d
f
e
d
f
D
Plagioclase
liquidus
de
ef

Liquid
solidus
Plagioclase
An
Ab
28
End of crystallization
a
1557
1500
b
Liquid
c
d
f
Plagioclase
1400
o
g
T C
h
plus
1300
Liquid
Plagioclase
1200
i
1118
1100
Ab
20
40
60
An
80
Weight An
29
a
1557
1500
b
Liquid
Numbers refer to the behavior of melts
observations
c
d
f
Plagioclase
1400
o
g
T C
h
plus
1300
Liquid
The actual temperatures and the range depend
on the bulk composition
Plagioclase
1200
i
1118
1100
Ab
20
40
60
An
80
Weight An
30
Melting--reverse of crystallization
  • Equilibrium melting is exactly the opposite
  • Heat An60 and the first melt is g at An20 and
    1340oC
  • Continue heating both melt and plagioclase
    change X
  • Last plagioclase to melt is c (An87) at 1475oC

a
1557
1500
b
Liquid
c
d
f
Plagioclase
1400
o
g
T C
h
plus
1300
Liquid
Plagioclase
1200
i
1118
1100
Ab
20
40
60
An
80
Weight An
31
Fractional crystallization
Fractional crystallization Remove crystals
as they form so they cant undergo a continuous
reaction with the melt At any T Xbulk Xliq due
to the removal of the crystals
a
1557
1500
b
Liquid
c
d
f
Plagioclase
1400
o
g
T C
h
plus
1300
Liquid
Plagioclase
1200
i
1118
1100
Ab
20
40
60
80
An
Weight An
32
Melting
a
1557
1500
b
Liquid
c
d
f
Plagioclase
1400
o
g
T C
h
plus
1300
Liquid
Plagioclase
1200
i
i
1118
1100
Ab
20
40
60
80
An
Weight An
33
Olivine System, another example
Isobaric T-X phase diagram at atmospheric
pressure (After Bowen and Shairer (1932), Amer.
J. Sci. 5th Ser., 24, 177-213.
34
C. Binary Peritectic Systems
Figure 6-12. Isobaric T-X phase diagram of the
system Fo-Silica at 0.1 MPa. After Bowen and
Anderson (1914) and Grieg (1927). Amer. J. Sci.
35
Immiscible Liquids
  • Cool X n
  • At 1960oC hit solvus
  • exsolution
  • 2 liquids o and p
  • f 2 F 1
  • both liquids follow solvus

36
D. Solid Solution with Eutectic Ab-Or (the
alkali feldspars)
Figure 6-16. T-X phase diagram of the system
albite-orthoclase at 0.2 GPa H2O pressure. After
Bowen and Tuttle (1950). J. Geology.
37
(No Transcript)
38
Effect of PH O on Ab-Or
2
Figure 6-17. The Albite-K-feldspar system at
various H2O pressures. (a) and (b) after Bowen
and Tuttle (1950), J. Geol, (c) after Morse
(1970) J. Petrol.
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