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ERSC 3P21 Metamorphic Petrology II 24/08/2011
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ERSC 3P21 - Brock University Greg Finn
Metamorphic Facies• Facies – ____________________________
________________________________________________________________________
• There is a predictable and common correspondence between the __________ of each rock and its ______________________
• Mineral _____________ that define the metamorphic _______ indicate that a state of stable _________ has been ________ over a restricted T and P condition.
ERSC 3P21 - Brock University Greg Finn
Metamorphic Facies• Several different facies have been formally
recognized and have been named according to distinct aspects of the facies– eg. greenschist = characterized by schists in
which green chlorite, talc, serpentine, epidote and actinolite are predominant
• Examine the mineralogical characteristics in metamorphosed mafic (basic) rocks subjected to prograde metamorphism
ERSC 3P21 - Brock University Greg Finn
Metamorphic GradeCalculatedGeothermalGradient
Watersaturatedgranitesolidus
Diagenesis
100
2
200 300 400 500 600 700 800 900 1000
14
12
10
8
6
4 10
20
30
40
Temperature (C)
Pres
sure
(kba
r)
Dep
th (k
m)
MEDIUMGRADE
HIGHGRADE
LOWGRADE
VERYLOW
GRADEor+ab+q
Liquid
mu + qor+Al2SiO5+H2O
ERSC 3P21 Metamorphic Petrology II 24/08/2011
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ERSC 3P21 - Brock University Greg Finn
Metamorphic FaciesCalculatedGeothermalGradient
Watersaturatedgranitesolidus
Diagenesis
100
2
200 300 400 500 600 700 800 900 1000
14
12
10
8
6
4 10
20
30
40
Temperature (C)
Pres
sure
(kba
r)
Dep
th (k
m)
Zeolite
PrehnitePumpellyite
GlaucophaneLawsonite
Greenschist
AmphiboliteGranulite
Eclogite
HornfelsPxHornfels Sanidinite
ERSC 3P21 - Brock University Greg Finn
Zeolite Facies
http://www.curiogrove.com/Zeolite/gfx/ze002.jpg
• Zeolites are a group of white to colourless _______ ________ silicates, analogous in composition to __________
• Common Zeolites are:• Laumontite - Ca(Al2Si4)O12·4H2O• Heulandite – (Ca,Na)2(Al2Si7)O18·6H2O• Analcime – NaAlSi2O6·H2O
• Assemblage qtz + heulandite + chlorite is diagnostic
http
://w
ww
.the-
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ce.c
om/2
005/
gold
2005
/imag
es/z
eolit
e.jp
g
ERSC 3P21 - Brock University Greg Finn
Prehnite - Pumpellyite Facies• Prehnite and pumpellyite, along
with the zeolites, commonly occur as _________ fillings in originally vesicular samples
• Minerals present are:• Prehnite – Ca2Al2Si3O10(OH)2
• Pumpellyite –Ca2MgAl2(SiO4)(Si2O7)(OH)2·H2O
• Assemblage qtz + Prehnite + Pumpellyite is diagnostic
http://www.asahi-net.or.jp/~ug7s-ktu/e_pumpel.htm
http
://w
ww
.dsu
per.n
et/~
mar
coue
t/im
ages
/pre
hnite
.jpg
ERSC 3P21 Metamorphic Petrology II 24/08/2011
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ERSC 3P21 - Brock University Greg Finn
Glaucophane - Lawsonite Facies
• AKA - ___________________• Minerals present are blue in colour• Glaucophane - Na2MgAl2Si8O22(OH)2• Lawsonite - CaAl2Si2O7(OH)2H2O • Jadeite – NaAlSi2O6
• Characteristic of regions of ______ and _________ metamorphism, near _____________ zones
• Assemblage jadeite + qtz + aragonite is diagnostic
ERSC 3P21 - Brock University Greg Finn
http://ic.ucsc.edu/~rocks/eart005/Metamorphic/Green_Blue.htm
http://www.tulane.edu/~sanelson/images/fransican.gif
http://geosciences.geol.u-psud.fr/ObjectifTerre/Mineralogie/mineropolarisant/Glaucophane/GlauLP.jpg
ERSC 3P21 - Brock University Greg Finn
• Formation of Blueschists
http://www.uwgb.edu/dutchs/graphic0/platetec/metzone.gif
From: http://www.uwgb.edu/dutchs/platetec/orogeny.htm
ERSC 3P21 Metamorphic Petrology II 24/08/2011
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ERSC 3P21 - Brock University Greg Finn
Metamorphic FaciesCalculatedGeothermalGradient
Watersaturatedgranitesolidus
Diagenesis
100
2
200 300 400 500 600 700 800 900 1000
14
12
10
8
6
4 10
20
30
40
Temperature (C)
Pres
sure
(kba
r)
Dep
th (k
m)
Zeolite
PrehnitePumpellyite
GlaucophaneLawsonite
ERSC 3P21 - Brock University Greg Finn
Greenschist Facies• A _______ schist developed through the
metamorphism of a ______-rich rock – basalt• Common minerals are:
• Epidote – Ca2Fe3+Al2OSi2O7(SiO4)(OH)• Actinolite – Ca2(Mg,Fe2+)5Si8O22(OH)2
• Chlorite – (Mg,Al,Fe)3(Si,Al)4O10(OH)2·(Mg,Al,Fe)3(OH)6
• Albite + Epidote + Actinolite + Chlorite + Calcite in mafic rocks
• Pyrophyllite in pelitic rocks
ERSC 3P21 - Brock University Greg Finn
ERSC 3P21 Metamorphic Petrology II 24/08/2011
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ERSC 3P21 - Brock University Greg Finn
Amphibolite Facies• Abundant _____ and little ____, as such they
do not produce quartz and micas• Named for abundant ____________• Common minerals are:
• Hornblende – Ca2(Mg,Fe,Al)5Si8O22(OH)2• Plagioclase – (Ca,Na)2(Al,Si)AlSi2)O8
» >An20
• Garnet – (Ca,Mg,Fe2+,Mn)3(Al,Fe3+,Cr)2(SiO4)3• Kyanite (Al2SiO5) in pelites
• Assemblage hornblende + plagioclase is diagnostic
ERSC 3P21 - Brock University Greg Finn
ERSC 3P21 - Brock University Greg Finn
a b
p
cpx
op
cpx
cpxcpx
oppp
pp
p
hbhb
hb hb
Sample 99-3 - Amphibolite (metamorphosed gabbro) under (a) plane light and (b) crossed polars. Minerals present include plagioclase (p), clinopyroxene (cpx) (note the variable colour (pleochroism) of the cpx brown and green), hornblende (hb) and opaques (op). (FOV = 8.5mm)
ERSC 3P21 Metamorphic Petrology II 24/08/2011
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ERSC 3P21 - Brock University Greg Finn
Metamorphic FaciesCalculatedGeothermalGradient
Watersaturatedgranitesolidus
Diagenesis
100
2
200 300 400 500 600 700 800 900 1000
14
12
10
8
6
4 10
20
30
40
Temperature (C)
Pres
sure
(kba
r)
Dep
th (k
m)
Zeolite
PrehnitePumpellyite
GlaucophaneLawsonite
GreenschistAmphibolite
ERSC 3P21 - Brock University Greg Finn
Granulite Facies• Characteristic of _____________• Cpx + Opx + Pl + (Fe,Mg) Garnet
ERSC 3P21 - Brock University Greg Finn
Eclogite Facies• Lower _____ or upper ______ (deepest
material sampled on a regular basis)• Feldspar-free assemblage,• Jadeite + pyrope (Mg garnet) is
diagnostic
ERSC 3P21 Metamorphic Petrology II 24/08/2011
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ERSC 3P21 - Brock University Greg Finn
garnet
garnet
gt
clinopyroxene
cpx
cpx
cpx
cpx
cpx
2.0 mm
garnet
garnet
gt
clinopyroxene
cpx
cpx
cpx
cpx
cpx2.0 mm
Sample PT-279: Eclogite. This sample is equivalent to the basalt, gabbro and amphibolite, except that it has been metamorphosed to a higher degree (~500-700°C and >10 kbars).This sample consists of medium to coarse grained clinopyroxene (cpx) which exhibits a weak green pleochroism and garnet (gt), an isotropic mineral. Hornblende, light green to dark green pleochroism, is present in this sample (not visible in this view). Minor amounts of plagioclase and quartz make up the fine grained matrix.
ERSC 3P21 - Brock University Greg Finn
Metamorphic FaciesCalculatedGeothermalGradient
Watersaturatedgranitesolidus
Diagenesis
100
2
200 300 400 500 600 700 800 900 1000
14
12
10
8
6
4 10
20
30
40
Temperature (C)
Pres
sure
(kba
r)
Dep
th (k
m)
Zeolite
PrehnitePumpellyite
GlaucophaneLawsonite
Greenschist
AmphiboliteGranulite
Eclogite
HornfelsPxHornfels Sanidinite
ERSC 3P21 - Brock University Greg Finn
Characteristics of regionally metamorphsed mudstones
Grade Rock Name Grain Size Key Minerals Features
Protolith Mudstone Very fine grained, clay sized particles
Clays, quartz Fissile, shale, bedding or massive, mudstone texture
Very Low Slate Very Fine, recrystallized particles
Clays, chlorite, quartz, Fe-oxides
Bedding, slaty cleavage
Low Phyllite Fine Micas, chlorite, quartz, Fe-oxides
Bedding, phyllitic foliation
Medium Schist Fine to medium, with random isolated large porphyrobalsts
Micas, chlorite, quartz, plag, garnet, staurolite, kyanite, Fe-Ti oxides
Schistosity, porphyroblasts, rare bedding
High Schist/gneiss Medium to coarse
Biotite, quartz, plag., garnet, cordierite, sillimanite, Fe-Ti oxides
Schistosity or gneissosity, segregation layering, porphyroblasts
Very High
Gneiss Medium to coarse
Biotite, quartz,plag., orthoclase, sillimanite, garnet, cordierite, Fe-Ti ox.
Gneissosity, segregation, layering, porphyroblasts, migmatitic layering