Post on 20-Jun-2020
transcript
Not all minerals present in a (metamorphic) rock are necessarily in equilibrium
an assemblage of minerals in mutual equilibrium is called a mineral paragenesis and a rock or thin-section can contain multiple equi assemblages or parageneses as relicts, overgrowths, inclusions, partial replacements etc. etc.
�15
Lecture 5: Mineral assemblage and paragenesis
Indicators of equilibrium:• minerals in direct contact, contacts are sharp and with correct crystal faces• mutual inclusions of A in B and B in A• ideal inter-mineral angles• …
Surface tension (or interfacial energy) generates a characteristic contact angle between minerals, also called the dihedral angle:
�16
Mineral assemblage and paragenesis
When Eint(A) = Eint(B), the angle is 120˚
When Eint(A) > Eint(B), the angle is less 120˚ so as to minimize the A-A interface length
figures from Winter (chapter 23)
Surface tension (or interfacial energy) generates a characteristic contact angle between minerals, also called the dihedral angle
�17
Mineral assemblage and paragenesis
c.
plag
plag
cpx
figure from Winter (chapter 23)
cpx
Assemblage and paragenesis
from Bucher and Frey 2002
two assemblages =two parageneses
one assemblage =two parageneses
one assemblage = one paragenesis
�18
Mineral assemblage and paragenesis
Not all minerals present in a (metamorphic) rock are necessarily in equilibrium
an assemblage of minerals in mutual equilibrium is called a mineral paragenesis and a rock or thin-section can contain multiple equi assemblages or parageneses as relicts, overgrowths, inclusions, partial replacements etc. etc.
This is a very important concept, because the succession of mineral paragene-ses provides information on the history of the rock and its metamorphic path
preservation of multiple generations of equilibrium mineral assemblages results from lower reaction rates resulting from a combination of lower temperatures, solid state reactions, lack of a fluid phase etc.
Igneous petrology focuses on the mineral paragenesis, metamorphic petrology on the history of the rock and its metamorphic path
�19
Mineral assemblage and paragenesis
prograde replacement retrograde replacement
with precursor minerals preserved: information on rock’s history �20
Mineral assemblage and paragenesis: an example
�21
chl ep ccpl q ru
chl ep pl ccdol q ru
amp chlpl q ilm
ampchl
ep pl
q ilm
chl ep ccpl q ilm
ampchl epgt q ilm
amp chl eppl gt q ilm
ampchl
ep ilm q
amp chl ccep gt q ilm
amp plgt ilm q
amp pl gtcpx ilm q
amp chl plgt q ilm
melt pl amp gt cpx
ilm q
900Temperature (oC)
Pres
sure
(kb
ar)
10001
3
5
7
9
500 600 700 800
2
4
6
8
Approxim
ate depth (km)
5
15
25
10
20
30
300 400
Sample 512256greenschist Nuuluk
amp pl gtcpx ilm q
amp pl gt cpx ilm
amp plgt ilm
chl ampdol plq ru amp pl
gt q ilm
chlamppl gtq ilm
chlamppl gt ilm
chl amppl q ilm
chl amppl dol gt
q ilm
chl amppl dolq ilm
chl plgt q
ilm dol
amp pl gtdol q ilm
amp chl plgt dol q ru
chl pl gtdol q ilm ru
melt amppl gt cpx
q ilm
meltamp plgt cpx
ilm
melt pl gtcpx ilm
melt plcpx ilm
melt gtcpx ilm
Pres
sure
(kb
ar)
Ti-Na-Ca-Fe-Mg-Al-Si-H-Osaturated in H2O-CO2 fluid
1
3
5
7
9
2
4
6
8
Approxim
ate depth (km)
5
15
25
10
20
30chlampdol
mgs pl ru q
chlampdolmgsab
q ru
chl ampdol abq ru
chl dolpl q ru
chl dolab q ru
chl dol pl qilm
chl dolpl q ru
ilm
Sample 512184greenstone Nuuluk
amp pl gtcpx ilm q
melt plgt cpxilm q melt
pl gtcpxilm
melt gt cpx q ilm
meltpl
cpx ilm
meltgt cpxilm
chl dolpl q ru
chl ep dolpl q ru
chl dolpl ilm q
dol chl amp plilm q
chl amppl ilm q
chl ep dolpl ilm q
dol chlamp pl qgt ilm
chl dolpl gtilm q
chl amppl gt ilm q
amp plgt ilm q
dol plgt ilm
q
dol amppl gt ilm q
dol amp pl gt cpxilm q
pl gt cpxilm q
Pres
sure
(kb
ar)
1
3
5
7
9
2
4
6
8
Approxim
ate depth (km)
5
15
25
10
20
30Sample 510866greenschist Nuuluk
ep
chl ep ccpl q ru
chl ep pl ccdol q ru
amp chlpl q ilm
ampchl
ep pl
q ilm
chl ep ccpl q ilm
ampchl epgt q ilm
amp chl eppl gt q ilm
ampchl
ep ilm q
amp chl ccep gt q ilm
amp plgt ilm q
amp pl gtcpx ilm q
amp chl plgt q ilm
melt pl amp gt cpx
ilm q
900Temperature (oC)
Pres
sure
(kb
ar)
10001
3
5
7
9
500 600 700 800
2
4
6
8
Approxim
ate depth (km)
5
15
25
10
20
30
300 400
Sample 512256greenschist Nuuluk
amp pl gtcpx ilm q
amp pl gt cpx ilm
amp plgt ilm
chl ampdol plq ru amp pl
gt q ilm
chlamppl gtq ilm
chlamppl gt ilm
chl amppl q ilm
chl amppl dol gt
q ilm
chl amppl dolq ilm
chl plgt q
ilm dol
amp pl gtdol q ilm
amp chl plgt dol q ru
chl pl gtdol q ilm ru
melt amppl gt cpx
q ilm
meltamp plgt cpx
ilm
melt pl gtcpx ilm
melt plcpx ilm
melt gtcpx ilm
Pres
sure
(kb
ar)
Ti-Na-Ca-Fe-Mg-Al-Si-H-Osaturated in H2O-CO2 fluid
1
3
5
7
9
2
4
6
8
Approxim
ate depth (km)
5
15
25
10
20
30chlampdol
mgs pl ru q
chlampdolmgsab
q ru
chl ampdol abq ru
chl dolpl q ru
chl dolab q ru
chl dol pl qilm
chl dolpl q ru
ilm
Sample 512184greenstone Nuuluk
amp pl gtcpx ilm q
melt plgt cpxilm q melt
pl gtcpxilm
melt gt cpx q ilm
meltpl
cpx ilm
meltgt cpxilm
chl dolpl q ru
chl ep dolpl q ru
chl dolpl ilm q
dol chl amp plilm q
chl amppl ilm q
chl ep dolpl ilm q
dol chlamp pl qgt ilm
chl dolpl gtilm q
chl amppl gt ilm q
amp plgt ilm q
dol plgt ilm
q
dol amppl gt ilm q
dol amp pl gt cpxilm q
pl gt cpxilm q
Pres
sure
(kb
ar)
1
3
5
7
9
2
4
6
8
Approxim
ate depth (km)
5
15
25
10
20
30Sample 510866greenschist Nuuluk
ep
ep
�22
Mineral assemblage and paragenesis: an example
�23
Mineral assemblage and paragenesis: an example
�24
Mineral assemblage and paragenesis: an example
�25
Mineral assemblage and paragenesis: an example
�26
chl ep ccpl q ru
chl ep pl ccdol q ru
amp chlpl q ilm
ampchl
ep pl
q ilm
chl ep ccpl q ilm
ampchl epgt q ilm
amp chl eppl gt q ilm
ampchl
ep ilm q
amp chl ccep gt q ilm
amp plgt ilm q
amp pl gtcpx ilm q
amp chl plgt q ilm
melt pl amp gt cpx
ilm q
900Temperature (oC)
Pres
sure
(kb
ar)
10001
3
5
7
9
500 600 700 800
2
4
6
8
Approxim
ate depth (km)
5
15
25
10
20
30
300 400
Sample 512256greenschist Nuuluk
amp pl gtcpx ilm q
amp pl gt cpx ilm
amp plgt ilm
chl ampdol plq ru amp pl
gt q ilm
chlamppl gtq ilm
chlamppl gt ilm
chl amppl q ilm
chl amppl dol gt
q ilm
chl amppl dolq ilm
chl plgt q
ilm dol
amp pl gtdol q ilm
amp chl plgt dol q ru
chl pl gtdol q ilm ru
melt amppl gt cpx
q ilm
meltamp plgt cpx
ilm
melt pl gtcpx ilm
melt plcpx ilm
melt gtcpx ilm
Pres
sure
(kb
ar)
Ti-Na-Ca-Fe-Mg-Al-Si-H-Osaturated in H2O-CO2 fluid
1
3
5
7
9
2
4
6
8
Approxim
ate depth (km)
5
15
25
10
20
30chlampdol
mgs pl ru q
chlampdolmgsab
q ru
chl ampdol abq ru
chl dolpl q ru
chl dolab q ru
chl dol pl qilm
chl dolpl q ru
ilm
Sample 512184greenstone Nuuluk
amp pl gtcpx ilm q
melt plgt cpxilm q melt
pl gtcpxilm
melt gt cpx q ilm
meltpl
cpx ilm
meltgt cpxilm
chl dolpl q ru
chl ep dolpl q ru
chl dolpl ilm q
dol chl amp plilm q
chl amppl ilm q
chl ep dolpl ilm q
dol chlamp pl qgt ilm
chl dolpl gtilm q
chl amppl gt ilm q
amp plgt ilm q
dol plgt ilm
q
dol amppl gt ilm q
dol amp pl gt cpxilm q
pl gt cpxilm q
Pres
sure
(kb
ar)
1
3
5
7
9
2
4
6
8
Approxim
ate depth (km)
5
15
25
10
20
30Sample 510866greenschist Nuuluk
ep
chl ep ccpl q ru
chl ep pl ccdol q ru
amp chlpl q ilm
ampchl
ep pl
q ilm
chl ep ccpl q ilm
ampchl epgt q ilm
amp chl eppl gt q ilm
ampchl
ep ilm q
amp chl ccep gt q ilm
amp plgt ilm q
amp pl gtcpx ilm q
amp chl plgt q ilm
melt pl amp gt cpx
ilm q
900Temperature (oC)
Pres
sure
(kb
ar)
10001
3
5
7
9
500 600 700 800
2
4
6
8
Approxim
ate depth (km)
5
15
25
10
20
30
300 400
Sample 512256greenschist Nuuluk
amp pl gtcpx ilm q
amp pl gt cpx ilm
amp plgt ilm
chl ampdol plq ru amp pl
gt q ilm
chlamppl gtq ilm
chlamppl gt ilm
chl amppl q ilm
chl amppl dol gt
q ilm
chl amppl dolq ilm
chl plgt q
ilm dol
amp pl gtdol q ilm
amp chl plgt dol q ru
chl pl gtdol q ilm ru
melt amppl gt cpx
q ilm
meltamp plgt cpx
ilm
melt pl gtcpx ilm
melt plcpx ilm
melt gtcpx ilm
Pres
sure
(kb
ar)
Ti-Na-Ca-Fe-Mg-Al-Si-H-Osaturated in H2O-CO2 fluid
1
3
5
7
9
2
4
6
8
Approxim
ate depth (km)
5
15
25
10
20
30chlampdol
mgs pl ru q
chlampdolmgsab
q ru
chl ampdol abq ru
chl dolpl q ru
chl dolab q ru
chl dol pl qilm
chl dolpl q ru
ilm
Sample 512184greenstone Nuuluk
amp pl gtcpx ilm q
melt plgt cpxilm q melt
pl gtcpxilm
melt gt cpx q ilm
meltpl
cpx ilm
meltgt cpxilm
chl dolpl q ru
chl ep dolpl q ru
chl dolpl ilm q
dol chl amp plilm q
chl amppl ilm q
chl ep dolpl ilm q
dol chlamp pl qgt ilm
chl dolpl gtilm q
chl amppl gt ilm q
amp plgt ilm q
dol plgt ilm
q
dol amppl gt ilm q
dol amp pl gt cpxilm q
pl gt cpxilm q
Pres
sure
(kb
ar)
1
3
5
7
9
2
4
6
8
Approxim
ate depth (km)
5
15
25
10
20
30Sample 510866greenschist Nuuluk
ep
�27
Mineral assemblage and paragenesis: an example
�28
Mineral assemblage and paragenesis: an example
�29
chl ep ccpl q ru
chl ep pl ccdol q ru
amp chlpl q ilm
ampchl
ep pl
q ilm
chl ep ccpl q ilm
ampchl epgt q ilm
amp chl eppl gt q ilm
ampchl
ep ilm q
amp chl ccep gt q ilm
amp plgt ilm q
amp pl gtcpx ilm q
amp chl plgt q ilm
melt pl amp gt cpx
ilm q
900Temperature (oC)
Pres
sure
(kb
ar)
10001
3
5
7
9
500 600 700 800
2
4
6
8
Approxim
ate depth (km)
5
15
25
10
20
30
300 400
Sample 512256greenschist Nuuluk
amp pl gtcpx ilm q
amp pl gt cpx ilm
amp plgt ilm
chl ampdol plq ru amp pl
gt q ilm
chlamppl gtq ilm
chlamppl gt ilm
chl amppl q ilm
chl amppl dol gt
q ilm
chl amppl dolq ilm
chl plgt q
ilm dol
amp pl gtdol q ilm
amp chl plgt dol q ru
chl pl gtdol q ilm ru
melt amppl gt cpx
q ilm
meltamp plgt cpx
ilm
melt pl gtcpx ilm
melt plcpx ilm
melt gtcpx ilm
Pres
sure
(kb
ar)
Ti-Na-Ca-Fe-Mg-Al-Si-H-Osaturated in H2O-CO2 fluid
1
3
5
7
9
2
4
6
8
Approxim
ate depth (km)
5
15
25
10
20
30chlampdol
mgs pl ru q
chlampdolmgsab
q ru
chl ampdol abq ru
chl dolpl q ru
chl dolab q ru
chl dol pl qilm
chl dolpl q ru
ilm
Sample 512184greenstone Nuuluk
amp pl gtcpx ilm q
melt plgt cpxilm q melt
pl gtcpxilm
melt gt cpx q ilm
meltpl
cpx ilm
meltgt cpxilm
chl dolpl q ru
chl ep dolpl q ru
chl dolpl ilm q
dol chl amp plilm q
chl amppl ilm q
chl ep dolpl ilm q
dol chlamp pl qgt ilm
chl dolpl gtilm q
chl amppl gt ilm q
amp plgt ilm q
dol plgt ilm
q
dol amppl gt ilm q
dol amp pl gt cpxilm q
pl gt cpxilm q
Pres
sure
(kb
ar)
1
3
5
7
9
2
4
6
8
Approxim
ate depth (km)
5
15
25
10
20
30Sample 510866greenschist Nuuluk
ep
chl ep ccpl q ru
chl ep pl ccdol q ru
amp chlpl q ilm
ampchl
ep pl
q ilm
chl ep ccpl q ilm
ampchl epgt q ilm
amp chl eppl gt q ilm
ampchl
ep ilm q
amp chl ccep gt q ilm
amp plgt ilm q
amp pl gtcpx ilm q
amp chl plgt q ilm
melt pl amp gt cpx
ilm q
900Temperature (oC)
Pres
sure
(kb
ar)
10001
3
5
7
9
500 600 700 800
2
4
6
8
Approxim
ate depth (km)
5
15
25
10
20
30
300 400
Sample 512256greenschist Nuuluk
amp pl gtcpx ilm q
amp pl gt cpx ilm
amp plgt ilm
chl ampdol plq ru amp pl
gt q ilm
chlamppl gtq ilm
chlamppl gt ilm
chl amppl q ilm
chl amppl dol gt
q ilm
chl amppl dolq ilm
chl plgt q
ilm dol
amp pl gtdol q ilm
amp chl plgt dol q ru
chl pl gtdol q ilm ru
melt amppl gt cpx
q ilm
meltamp plgt cpx
ilm
melt pl gtcpx ilm
melt plcpx ilm
melt gtcpx ilm
Pres
sure
(kb
ar)
Ti-Na-Ca-Fe-Mg-Al-Si-H-Osaturated in H2O-CO2 fluid
1
3
5
7
9
2
4
6
8
Approxim
ate depth (km)
5
15
25
10
20
30chlampdol
mgs pl ru q
chlampdolmgsab
q ru
chl ampdol abq ru
chl dolpl q ru
chl dolab q ru
chl dol pl qilm
chl dolpl q ru
ilm
Sample 512184greenstone Nuuluk
amp pl gtcpx ilm q
melt plgt cpxilm q melt
pl gtcpxilm
melt gt cpx q ilm
meltpl
cpx ilm
meltgt cpxilm
chl dolpl q ru
chl ep dolpl q ru
chl dolpl ilm q
dol chl amp plilm q
chl amppl ilm q
chl ep dolpl ilm q
dol chlamp pl qgt ilm
chl dolpl gtilm q
chl amppl gt ilm q
amp plgt ilm q
dol plgt ilm
q
dol amppl gt ilm q
dol amp pl gt cpxilm q
pl gt cpxilm q
Pres
sure
(kb
ar)
1
3
5
7
9
2
4
6
8
Approxim
ate depth (km)
5
15
25
10
20
30Sample 510866greenschist Nuuluk
ep
ep
�30
Mineral assemblage and paragenesis
Sequence of metamorphic mineral parageneses in one thin-section:
1. Present as inclusions in garnet: amphibole + rutile + epidote
2. Main mineral stage: garnet + amphibole + ilmenite + quartz + plagioclase
3. Replacement at grain edges: amphibole to biotite
4. Locally on plagioclase grains: plagioclase going to albite
A metamorphic P-T path reconstructed from prograde, peak and retrograde mineral parageneses, all of which are subsets of the rock mineral assemblage
�31
chl ep ccpl q ru
chl ep pl ccdol q ru
amp chlpl q ilm
ampchl
ep pl
q ilm
chl ep ccpl q ilm
ampchl epgt q ilm
amp chl eppl gt q ilm
ampchl
ep ilm q
amp chl ccep gt q ilm
amp plgt ilm q
amp pl gtcpx ilm q
amp chl plgt q ilm
melt pl amp gt cpx
ilm q
900Temperature (oC)
Pres
sure
(kb
ar)
10001
3
5
7
9
500 600 700 800
2
4
6
8
Approxim
ate depth (km)
5
15
25
10
20
30
300 400
Sample 512256greenschist Nuuluk
amp pl gtcpx ilm q
amp pl gt cpx ilm
amp plgt ilm
chl ampdol plq ru amp pl
gt q ilm
chlamppl gtq ilm
chlamppl gt ilm
chl amppl q ilm
chl amppl dol gt
q ilm
chl amppl dolq ilm
chl plgt q
ilm dol
amp pl gtdol q ilm
amp chl plgt dol q ru
chl pl gtdol q ilm ru
melt amppl gt cpx
q ilm
meltamp plgt cpx
ilm
melt pl gtcpx ilm
melt plcpx ilm
melt gtcpx ilm
Pres
sure
(kb
ar)
Ti-Na-Ca-Fe-Mg-Al-Si-H-Osaturated in H2O-CO2 fluid
1
3
5
7
9
2
4
6
8
Approxim
ate depth (km)
5
15
25
10
20
30chlampdol
mgs pl ru q
chlampdolmgsab
q ru
chl ampdol abq ru
chl dolpl q ru
chl dolab q ru
chl dol pl qilm
chl dolpl q ru
ilm
Sample 512184greenstone Nuuluk
amp pl gtcpx ilm q
melt plgt cpxilm q melt
pl gtcpxilm
melt gt cpx q ilm
meltpl
cpx ilm
meltgt cpxilm
chl dolpl q ru
chl ep dolpl q ru
chl dolpl ilm q
dol chl amp plilm q
chl amppl ilm q
chl ep dolpl ilm q
dol chlamp pl qgt ilm
chl dolpl gtilm q
chl amppl gt ilm q
amp plgt ilm q
dol plgt ilm
q
dol amppl gt ilm q
dol amp pl gt cpxilm q
pl gt cpxilm q
Pres
sure
(kb
ar)
1
3
5
7
9
2
4
6
8
Approxim
ate depth (km)
5
15
25
10
20
30Sample 510866greenschist Nuuluk
ep
chl ep ccpl q ru
chl ep pl ccdol q ru
amp chlpl q ilm
ampchl
ep pl
q ilm
chl ep ccpl q ilm
ampchl epgt q ilm
amp chl eppl gt q ilm
ampchl
ep ilm q
amp chl ccep gt q ilm
amp plgt ilm q
amp pl gtcpx ilm q
amp chl plgt q ilm
melt pl amp gt cpx
ilm q
900Temperature (oC)
Pres
sure
(kb
ar)
10001
3
5
7
9
500 600 700 800
2
4
6
8
Approxim
ate depth (km)
5
15
25
10
20
30
300 400
Sample 512256greenschist Nuuluk
amp pl gtcpx ilm q
amp pl gt cpx ilm
amp plgt ilm
chl ampdol plq ru amp pl
gt q ilm
chlamppl gtq ilm
chlamppl gt ilm
chl amppl q ilm
chl amppl dol gt
q ilm
chl amppl dolq ilm
chl plgt q
ilm dol
amp pl gtdol q ilm
amp chl plgt dol q ru
chl pl gtdol q ilm ru
melt amppl gt cpx
q ilm
meltamp plgt cpx
ilm
melt pl gtcpx ilm
melt plcpx ilm
melt gtcpx ilm
Pres
sure
(kb
ar)
Ti-Na-Ca-Fe-Mg-Al-Si-H-Osaturated in H2O-CO2 fluid
1
3
5
7
9
2
4
6
8
Approxim
ate depth (km)
5
15
25
10
20
30chlampdol
mgs pl ru q
chlampdolmgsab
q ru
chl ampdol abq ru
chl dolpl q ru
chl dolab q ru
chl dol pl qilm
chl dolpl q ru
ilm
Sample 512184greenstone Nuuluk
amp pl gtcpx ilm q
melt plgt cpxilm q melt
pl gtcpxilm
melt gt cpx q ilm
meltpl
cpx ilm
meltgt cpxilm
chl dolpl q ru
chl ep dolpl q ru
chl dolpl ilm q
dol chl amp plilm q
chl amppl ilm q
chl ep dolpl ilm q
dol chlamp pl qgt ilm
chl dolpl gtilm q
chl amppl gt ilm q
amp plgt ilm q
dol plgt ilm
q
dol amppl gt ilm q
dol amp pl gt cpxilm q
pl gt cpxilm q
Pres
sure
(kb
ar)
1
3
5
7
9
2
4
6
8
Approxim
ate depth (km)
5
15
25
10
20
30Sample 510866greenschist Nuuluk
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