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Metamorphic RocksMetamorphic Rocks
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METAMORPHIC ROCKSMETAMORPHIC ROCKS
Metamorphic rocks areMetamorphic rocks are changed rockschanged rocks TheThe protolithprotolith (the(the parent rockparent rock ) is the) is the
preexisting rock from which thepreexisting rock from which themetamorphic rock was formedmetamorphic rock was formed
They areThey are formed in the solid stateformed in the solid state inin
response to the followingresponse to the following principalprincipalagents of metamorphismagents of metamorphism ::
Change inChange in pressurepressure Change inChange in temperaturetemperature
Change inChange in pressurepressure andand temperaturetemperature
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Formation of Metamorphic RocksFormation of Metamorphic Rocks
Metamorphisme
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METAMORPHIC ROCKSMETAMORPHIC ROCKS
Metamorphism may cause a change in a rockMetamorphism may cause a change in a rock s:s:
Structure/TextureStructure/Texture
Mineral assemblageMineral assemblage Composition (slightly)Composition (slightly)
All of the aboveAll of the above
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Factors That Control the Characteristics ofFactors That Control the Characteristics ofMetamorphic RocksMetamorphic Rocks
1.1. ProtolithProtolith CompositionComposition
2.2. PressurePressure
3.3. TemperatureTemperature
4.4. TimeTime
C C f
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Factors That Control the Characteristics ofFactors That Control the Characteristics ofMetamorphic RocksMetamorphic Rocks
1.1. ProtolithProtolith CompositionComposition
MaficMafic protolithsprotoliths (basalt,(basalt, diabasediabase, and, and gabbrogabbro))
yield a dark charcoal grayyield a dark charcoal gray maficmafic metamorphicmetamorphic
rock calledrock called amphiboliteamphibolite
FelsicFelsic protolithsprotoliths (granite,(granite, rhyoliterhyolite, mudstone,, mudstone,
sandstone, conglomerate,sandstone, conglomerate, brecciabreccia) yield light) yield light
colored tan, silver, light to medium gray, etc.colored tan, silver, light to medium gray, etc.
felsicfelsic metamorphic rocksmetamorphic rocks
F Th C l h Ch i i fF t Th t C t l th Ch t i ti f
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Factors That Control the Characteristics ofFactors That Control the Characteristics ofMetamorphic RocksMetamorphic Rocks
2. Pressure (stress)
Increasing pressure flattens grains, crushesgrains (reduces size), causes shearing
Confining pressure, associated with depth ofburial, is equal in all directions
Differential pressure is not equal in all
directions Produces foliation (parallel alignment of
grains)
Pure shear = compression, flattens grains Simple shear = skewing, stretches grains,
produces lineation, aligns elongate grains
in direction of transport
F t Th t C t l th Ch t i ti fF t Th t C t l th Ch t i ti f
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Factors That Control the Characteristics ofFactors That Control the Characteristics ofMetamorphic RocksMetamorphic Rocks
Confining PressureConfining Pressure
Pressure is equal inPressure is equal in
all directionsall directions
F t Th t C t l th Ch t i ti fF t Th t C t l th Ch t i ti f
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Factors That Control the Characteristics ofFactors That Control the Characteristics ofMetamorphic RocksMetamorphic Rocks
Differential PressureDifferential Pressure Differential pressureDifferential pressure
IsIs notnot equal in all directionsequal in all directions
Leads toLeads to formation of foliationformation of foliation by eitherby either
Pure shear (flattening)Pure shear (flattening)
Simple shear (skewing)Simple shear (skewing)
Pure shear (flattening)Pure shear (flattening) Simple shear (skewing)Simple shear (skewing)
F t Th t C t l th Ch t i ti fFactors That Control the Characteristics of
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Factors That Control the Characteristics ofFactors That Control the Characteristics ofMetamorphic RocksMetamorphic Rocks
Type of foliationType of foliation
Slaty Cleavage Alignment of small micaflakes
Schistosity Alignment of large mica
flakes
Gneissic Banding segregation of felsic
and mafic minerals into alternating lightand dark bands
Factors That Control the Characteristics ofFactors That Control the Characteristics of
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Bedding is perpendicular to cleavage
at the top and bottom of the fold
Foliation: Development of Slaty CleavageFoliation: Development of Slaty Cleavage
Factors That Control the Characteristics ofFactors That Control the Characteristics ofMetamorphic RocksMetamorphic Rocks
Factors That Control the Characteristics ofFactors That Control the Characteristics of
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Factors That Control the Characteristics ofFactors That Control the Characteristics ofMetamorphic RocksMetamorphic Rocks
Foliation: Development of SchistosityFoliation: Development of Schistosity
http://www.tulane.edu/~sanelson/geol212/contactmeta.htm
Factors That Control the Characteristics ofFactors That Control the Characteristics of
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Factors That Control the Characteristics ofFactors That Control the Characteristics ofMetamorphic RocksMetamorphic Rocks
Foliation: Formation of Gneissic BandingFoliation: Formation of Gneissic Banding
Factors That Control the Characteristics ofFactors That Control the Characteristics of
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Factors That Control the Characteristics ofFactors That Control the Characteristics ofMetamorphic RocksMetamorphic Rocks
3.3. TemperatureTemperature
Increasing temperatureIncreasing temperature causes increasedcauses increased
movement of ions which in turn causesmovement of ions which in turn causes Mineral grains to grow largerMineral grains to grow larger
New minerals to form moving up BowensNew minerals to form moving up Bowens
Reaction SeriesReaction Series Minerals toMinerals to recrystallizerecrystallize
Decreasing temperatureDecreasing temperature causes new mineralscauses new minerals
to form moving down Bowens Reaction seriesto form moving down Bowens Reaction series The upper limit on T for metamorphism isThe upper limit on T for metamorphism is
partial meltingpartial melting
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Tempe
rature&
pressuredecreases
Temperature&pressureincreases
Olivine
Pyroxene
Amphibole
Biotite
Ca-rich
Na-rich
Ca-Na-rich
Na-Ca-rich
Quartz
Musc
ovite
K-feldspar P
lagi
oc
lase
fe
lds
par
BOWENS REACTION SERIES
1200C
700C
High
Intermediate
Low
The Effect of Temperature Changes on Composition and MetamorphisThe Effect of Temperature Changes on Composition and Metamorphismm
MAFIC
INTM
FELSIC
Factors That Control the Characteristics ofFactors That Control the Characteristics of
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4. Time Metamorphic reactions and textural changes
require mill ions of years to occur
Factors That Control the Characteristics ofFactors That Control the Characteristics ofMetamorphic RocksMetamorphic Rocks
Index Minerals of Metamorphic RocksIndex Minerals of Metamorphic Rocks
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Index Minerals of Metamorphic RocksIndex Minerals of Metamorphic RocksIndex MineralsIndex Minerals
Chlorite Biotite Almandite (garnet) Staurolite
Andalusite Kyanite Sillimanite
Not specificNot specific Quartz Plagioclase
Orthoclase Biotite Muscovite Hornblende Calcite Dolomite
Sillim
anite
Biotite
Chlo
rite
And
alusite
Ky
anite
Alm
a
ndite
(Garn
et)
Staurolite
MetamorphicMetamorphic FaciesFacies
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MetamorphicMetamorphic FaciesFacies
o
Classification of Metamorphic RocksClassification of Metamorphic Rocks
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Classification of Metamorphic RocksClassification of Metamorphic Rocks
1. Regional metamorphic rocks
Form in response to increased temperatureand directed pressure along plate boundaries
Are foliated
Were sheared by pure shear or simple shear
2. Contact metamorphic rocks
Form in response to contact with magma athigh T and /or high confining P
Found adjacent to igneous intrusions
Are usually unfoliated
Where do the metamorphic rocks form?Where do the metamorphic rocks form?
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Where do the metamorphic rocks form?Where do the metamorphic rocks form?
Classification of Metamorphic RocksClassification of Metamorphic Rocks
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Formation ofFormation ofRegional MetamorphicRegional Metamorphic
RocksRocks
Classification of Metamorphic RocksClassification of Metamorphic Rocks
Formation ofFormation of
Contact MetamorphicContact Metamorphic
RocksRocks
Classification of Metamorphic RocksClassification of Metamorphic Rocks
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Contact metamorphic rocksRegional metamorphic rocks
Classification of Metamorphic RocksClassification of Metamorphic Rocks
Classification of Metamorphic RocksClassification of Metamorphic Rocks
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C ass ca o o e a o p c oc sC ass ca o o e a o p c oc sFormation of Contact Metamorphic RocksFormation of Contact Metamorphic Rocks
ProtolithProtolith and Metamorphic Rocksand Metamorphic Rocks
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pp
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Perubahan TexturFoliasiSlaty CleavageSekistositasCompositional Banding
FOLIASI
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FOLIASI
YATIDAK
UKURAN BUTIR
SangatHalus Halus Sedang Kasar
Sekis GenisKuarsit
Migmatik
Filit MilonitPilonit
Eklogit SlateAmfibolit GranulitHornfels Marmer
KasarSedang-halus
UKURAN BUTIR
Mineral Utama?Keras?
YA Amfibol Kalsit Kuarsa GarnetPiroksen
FeldsparPiroksen
Keras?
PucatKataklstik
Kehijauan
Schistosity GneissoreSlaty Cleavage
Types of Metamorphic RocksTypes of Metamorphic Rocks
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Are formed by differential pressure (pure shear, simple shear)
SlateDull, microscopic grains, strong slaty cleavage, anycolor, mudstone protolith
Phyllite
Shiny, strongly micaceous with microscopic grains,strong schistosity, cleavage, can be mafic or felsic, anyrock-type protolith
Schist
Shiny, strongly micaceous, fine to medium grained,strong schistosity, cleavage, any color, any rock-typeprotolith
Gneiss
Dull, weakly micaceous, fine to coarse grained, banded,
weak cleavage, any rock-type protolith, but most oftensheared coarse grained protolith such as granite,conglomerate, breccia
Migmatite
Dull, weakly micaceous, fine to coarse grained, foldedbanded texture, weak cleavage, almost melted, any rock-type protolith
A. Foliated Metamorphic RocksA. Foliated Metamorphic Rocks
yp pyp p
Types of Metamorphic RocksTypes of Metamorphic Rocks
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Protolith:Protolith: Fine grained rock likeFine grained rock likeshale, mudstone, or siltstoneshale, mudstone, or siltstone
SlateSlate
Appearance:Appearance: Dull, microscopicDull, microscopicgrains, strong slaty cleavage,grains, strong slaty cleavage,
any colorany color
yp p
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Slate (Batusabak)
Types of Metamorphic RocksTypes of Metamorphic Rocks
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PhyllitePhyllite
Appearance:Appearance: Shiny, stronglyShiny, stronglymicaceousmicaceous withwith microscopicmicroscopic
grainsgrains , has strong schistose, has strong schistose
cleavage, can be felsiccleavage, can be felsic
(muscovite(muscovite--rich, silvery) orrich, silvery) orMafic (Mafic (biotitebiotite--rich, shinyrich, shiny
medium to dark gray)medium to dark gray)
Protolith:Protolith: Can be any rockCan be any rock--typetype
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FILIT MIKA
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SEKIS KLORITOID
Types of Metamorphic RocksTypes of Metamorphic Rocks
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SchistSchist
Appearance:Appearance: Shiny, stronglyShiny, stronglymicaceousmicaceous, fine to medium grained, fine to medium grained
has strong schistose cleavage,has strong schistose cleavage,
can be felsic (muscovitecan be felsic (muscovite--rich,rich,
silvery) or mafic (silvery) or mafic (biotitebiotite--rich,rich,shiny medium to dark gray)shiny medium to dark gray)
Protolith:Protolith: Can be any rockCan be any rock--typetype
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SEKIS
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SEKIS
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SEKIS GARNET-MIKA
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MILONIT
Types of Metamorphic RocksTypes of Metamorphic Rocks
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GneissGneiss
Protolith:Protolith: Can be any rockCan be any rock--type,type, but
most often formed from a sheared
coarse grained protolith such asgranite, conglomerate, breccia
Appearance:Appearance: Dull, weakly micaceous,
fine to coarse grained, banded, weak
cleavage
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GENIS-MIGMATIT
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GENES
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GENIS
Types of Metamorphic RocksTypes of Metamorphic Rocks
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MigmatiteMigmatite
Protolith:Protolith: Can be any rockCan be any rock--typetype
Appearance:Appearance: Dull, weakly micaceous,
fine to coarse grained, folded banded
texture, weak cleavage, almost melted,
a folded gneiss
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MIGMATIT
B Special Types of Metamorphic RocksB Special Types of Metamorphic Rocks
Types of Metamorphic RocksTypes of Metamorphic Rocks
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B. Special Types of Metamorphic RocksB. Special Types of Metamorphic Rocks
May be foliated or unfoliated Quartzite
Metamorphosed sandstone
Harder than marble Will not fizz (release CO2) in the presence of acid
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METAPSAMIT(META BATUPASIR)
B. Special Types of Metamorphic RocksB. Special Types of Metamorphic Rocks
Types of Metamorphic RocksTypes of Metamorphic Rocks
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B. Special Types of Metamorphic Rocksp yp p
Marble
Metamorphosed limestone
Contains calcium carbonate
Will f izz (release CO2) in the presence of acid
Softer than quartzite
May be foliated or unfoliated
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MARMER
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MARMER
B. Special Types of Metamorphic RocksB. Special Types of Metamorphic RocksTypes of Metamorphic RocksTypes of Metamorphic Rocks
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p yp pp yp p
AmphiboliteMay be foliated or unfoliated
Dull black, fine to coarse grained, weak cleavage if
sheared (gneissic) Metamorphosed gabbro, basalt, or diorite
Dark rock composed mostly of amphibole and Ca-Na plagioclase, may be
either foliated or unfoliated, often with large (visible) elongated crystals ofamphibole
http://www.smccd.net/accounts/hand/geology101/metamorphic/images/amphibolite2.jpghttp://www.smccd.net/accounts/hand/geology101/metamorphic/images/amphibolite2.jpghttp://www.smccd.net/accounts/hand/geology101/metamorphic/images/amphibolite2.jpghttp://www.smccd.net/accounts/hand/geology101/metamorphic/images/amphibolite2.jpghttp://www.smccd.net/accounts/hand/geology101/metamorphic/images/amphibolite1.jpg7/28/2019 Modul 8 - Metamorphic Rocks
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SKARN
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EKLOGIT
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EKLOGIT