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Metamorphic Rocks
Metamorphic Rocks
and M
etamorphic Processes
and M
etamorphic Processes
Metamorphic Rocks
Metamorphic Rocks
��Metamorphic rocks form
from pre
Metamorphic rocks form
from pre-- existing rocks
existing rocks
��Metamorphic rocks change with increasing
Metamorphic rocks change with increasing
temperature (and pressure to a lesser extent)
temperature (and pressure to a lesser extent)
due to chemical reactions between m
inerals
due to chemical reactions between m
inerals
��Metamorphic reactions are
Metamorphic reactions are isochemical
isochemical
��The m
inerals present in a given m
etamorphic
The m
inerals present in a given m
etamorphic
rocks will depend both on its composition and
rocks will depend both on its composition and
the conditions under which it was
the conditions under which it was
metamrophosed
metamrophosed(P and T)
(P and T)
Typical Composition of Rocks
Typical Composition of Rocks
0.05
0.05
0.24
0.24
3.96
3.96
4.30
4.30
1.10
1.10
0.34
0.34
KK22OO
0.03
0.03
0.07
0.07
1.13
1.13
3.55
3.55
2.91
2.91
0.49
0.49
Na
Na22OO
32.87
32.87
53.06
53.06
3.50
3.50
1.14
1.14
9.47
9.47
5.05
5.05
CaO
CaO
21.88
21.88
1.59
1.59
2.82
2.82
0.39
0.39
6.73
6.73
31.24
31.24
MgO
MgO
0.05
0.05
0.07
0.07
0.25
0.25
0.06
0.06
0.20
0.20
0.41
0.41
MnO
MnO
0.60
0.60
1.15
1.15
5.69
5.69
1.59
1.59
10.92
10.92
11.19
11.19
FeO
FeO
0.13
0.13
0.98
0.98
17.00
17.00
13.27
13.27
15.74
15.74
4.23
4.23
AlAl 22OO33
0.41
0.41
3.64
3.64
64.70
64.70
72.82
72.82
49.20
49.20
42.26
42.26
SiOSiO
22
Dolostone
Dolostone
Limestone
Limestone
Shale
Shale
Granite
Granite
Gabbro
Gabbro
Peridotite
Peridotite
What ele
ments
are
ES
SE
NTIA
L to d
escribe e
ach rock?
Typical Composition of Rocks
Typical Composition of Rocks
0.05
0.05
0.24
0.24
3.96
3.96
4.30
4.30
1.10
1.10
0.34
0.34
KK22OO
0.03
0.03
0.07
0.07
1.13
1.13
3.55
3.55
2.91
2.91
0.49
0.49
Na
Na22OO
32.87
32.87
53.06
53.06
3.50
3.50
1.14
1.14
9.47
9.47
5.05
5.05
CaO
CaO
21.88
21.88
1.59
1.59
2.82
2.82
0.39
0.39
6.73
6.73
31.24
31.24
MgO
MgO
0.05
0.05
0.07
0.07
0.25
0.25
0.06
0.06
0.20
0.20
0.41
0.41
MnO
MnO
0.60
0.60
1.15
1.15
5.69
5.69
1.59
1.59
10.92
10.92
11.19
11.19
FeO
FeO
0.13
0.13
0.98
0.98
17.00
17.00
13.27
13.27
15.74
15.74
4.23
4.23
AlAl 22OO33
0.41
0.41
3.64
3.64
64.70
64.70
72.82
72.82
49.20
49.20
42.26
42.26
SiOSiO
22
Dolostone
Dolostone
Limestone
Limestone
Shale
Shale
Granite
Granite
Gabbro
Gabbro
Peridotite
Peridotite
2
Essential Components of Rocks
Essential Components of Rocks
CaO
CaO
KK22OO
CaO
CaO
CaO
CaO
KK22OO
CaO
CaO
FeO
FeO
Na
Na22OO
FeO
FeO
MgO
MgO
MgO
MgO
Al
Al 22OO33
Al
Al 22OO33
Al
Al 22OO33
FeO
FeO
SiOSiO
22SiOSiO
22SiOSiO
22SiOSiO
22SiOSiO
22
Carbonate
Carbonate
Rock
Rock
Shale
Shale
Granite
Granite
Gabbro
Gabbro
Peridotite
Peridotite
Chemographic
Chemographic
Analysis:
Analysis:
SiO
SiO
22-- C
aO
CaO-- M
gO Diagrams
MgO Diagrams
Chemographic
Chemographic
Analysis:
Analysis:
ACF Diagrams
ACF Diagrams
Chemographics
Chemographics
��What minerals (pink dots) would you need to have to in a
What minerals (pink dots) would you need to have to in a
rock with composition X? Y?
rock with composition X? Y?
Fig. 26-12.From W
inter (2001) An
Introduction to Igneous and
Metamorphic Petrology. Prentice
Hall.
Y
3
Chemographic
Chemographic
Analysis:
Analysis:
SiO
SiO
22-- C
aO
CaO-- M
gO Diagrams
MgO Diagrams
“Rock A”
What m
inera
ls m
ight you fin
d in a
rock w
ith c
om
positio
n “A
”?
Chemographic
Chemographic
Analysis:
Analysis:
SiO
SiO
22-- C
aO
CaO-- M
gO Diagrams
MgO Diagrams
What m
inera
ls m
ight you fin
d in a
rock w
ith c
om
positio
n “B
”?
“Rock B”
Chemographic
Chemographic
Analysis:
Analysis:
ACF Diagrams
ACF Diagrams
What m
inera
ls m
ight you fin
d in a
rock w
ith c
om
positio
n “C
”?
Rock C
Chemographic
Chemographic
Analysis
Analysis
��There can be m
any combinations of minerals for
There can be m
any combinations of minerals for
a given rock composition that are
a given rock composition that are
chemographically
chemographically
allo
wable
allo
wable……
��Are
they a
ll pro
bable
, or even p
ossib
le?
Are
they a
ll pro
bable
, or even p
ossib
le?
Many a
re, but m
any a
re n
ot. If you u
nders
tand
Many a
re, but m
any a
re n
ot. If you u
nders
tand
the b
asic
s o
f m
eta
morp
hic
pro
cesses y
ou c
an
the b
asic
s o
f m
eta
morp
hic
pro
cesses y
ou c
an
reason s
om
e h
ighly
pro
bable
and h
ighly
re
ason s
om
e h
ighly
pro
bable
and h
ighly
im
pro
bable
com
bin
ations.
impro
bable
com
bin
ations.
4
General Rules of Metamorphism
General Rules of Metamorphism
��Metamorphism is
Metamorphism is isochemical
isochemicalwith respect to non
with respect to non-- volatile
volatile
components(H
components(H
22O and CO
O and CO
22))
��Most metamorphic reactions liberate volatiles (H
Most metamorphic reactions liberate volatiles (H
22O and
O and
CO
CO
22))
��The m
inerals in low
The m
inerals in low-- grade m
etamorphic rocks have m
ore
grade m
etamorphic rocks have m
ore
volatiles than high
volatiles than high-- grade m
etamorphic rocks
grade m
etamorphic rocks
��e.g., m
icas
e.g., m
icas ��
amphiboles
amphiboles ��
pyroxenes
pyroxenes
��Increasing m
etamorphic grade generally corresponds to
Increasing m
etamorphic grade generally corresponds to
increasing grain size
increasing grain size
��e.g., clays
e.g., clays ��
micas
micas
Chemographic
Chemographic
Analysis:
Analysis:
ACF Diagrams
ACF Diagrams
Metamorphic M
ineral Assemblages in
Metamorphic M
ineral Assemblages in
the Field
the Field
Metamorphic Facies
Metamorphic Facies
��A set of metamorphic m
ineral
A set of metamorphic m
ineral
assemblages that are repeatedly
assemblages that are repeatedly
associated in space and tim
e, such that
associated in space and tim
e, such that
there is predictable relation between
there is predictable relation between
mineral assemblage, chemical
mineral assemblage, chemical
composition, and m
etamorphic conditions
composition, and m
etamorphic conditions
5
Metamorphic Facies
Metamorphic Facies
Progressive M
etamorphism of
Progressive M
etamorphism of Metabasites
Metabasites
Chemographic
Chemographic
Analysis:
Analysis:
SiO
SiO
22-- C
aO
CaO-- M
gO Diagrams
MgO Diagrams
Progressive M
etamorphism of Carbonate Rocks
Progressive M
etamorphism of Carbonate Rocks
6
Metamorphic Texture Changes
Metamorphic Texture Changes
Quartz Arenite
Quartzite
Metamorphic Texture Changes
Metamorphic Texture Changes
Quartz Arenite
Quartzite
Lim
estone
Marble
Metamorphic Texture Changes
Metamorphic Texture Changes
Granite
Gneiss
Metamorphic Texture Changes
Metamorphic Texture Changes
Shale
Slate
Schist
Gneiss
