ERSC 3P21 Metamorphic II HO.ppt - Brock University › ... › sites › 106 › ERSC-3P21-Metamorphic_II.pdf · ERSC 3P21 Metamorphi c Petrology II 24/08/2011 2 ERSC 3P21 - Brock

ERSC 3P21 Metamorphic Petrology II 24/08/2011

1

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.


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


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


2


Metamorphic FaciesCalculatedGeothermalGradient


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


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-

conf

eren

ce.c

om/2

005/

gold

2005

/imag

es/z

eolit

e.jp

g


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


3


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


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


• Formation of Blueschists

http://www.uwgb.edu/dutchs/graphic0/platetec/metzone.gif

From: http://www.uwgb.edu/dutchs/platetec/orogeny.htm


4




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



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



5


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



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)


6




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


GreenschistAmphibolite


Granulite Facies• Characteristic of _____________• Cpx + Opx + Pl + (Fe,Mg) Garnet


Eclogite Facies• Lower _____ or upper ______ (deepest

material sampled on a regular basis)• Feldspar-free assemblage,• Jadeite + pyrope (Mg garnet) is

diagnostic


7


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.




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


Greenschist

AmphiboliteGranulite

Eclogite

HornfelsPxHornfels Sanidinite


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

ERSC 3P21 Metamorphic II HO.ppt - Brock University › ... › sites › 106 › ERSC-3P21-Metamorphic_II.pdf · ERSC 3P21 Metamorphi c Petrology II 24/08/2011 2 ERSC 3P21 - Brock

Documents