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Metamorfisme dan
batuan metamorfik
HOW
WHERE
CONTACT
METAMORFISME
JENIS
REGIONAL/
DYNAMIC
PREEXISTING
ROCKS
T, P, CHEMICAL
FLUIDS
BATUAN
METAMORFIK
HOW
WHERE
JENIS BATUAN
& CIRI KEJURUTERAAN
LINEATION
TEXTURE
FOLIATION
CHANGES
MINERALOGY
NONFOLIATED
Metamorphism means
"changed form“ (berubah
bentuk)
Kitar batuan (Rock cycle)
CYCLE
Batuan Metamorfik terjadi
hasil drpd perubahan suhu,
tekanan dan bendalir kimia
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Agents of Metamorphism
Changes occur because of:
Heat
Pressure
Chemical fluids
Perubahan suhu:
Geothermal gradient
Temperature increases with depth at
a rate of 20 - 30 degrees C per km in
the crust.
Ultimate source of the heat?
Radioactive decay. Increase of
temperature and pressure with
depth causes Regional
Metamorphism (Metamorfisme
Rantau)
Heat may come from large bodies of
molten rock rising under a wide
geographic area.
Metamorfisme sentuh
• Intrusions of hot magma can
bake rocks as it intrudes them.
Lava flows can also bake rocks
on the ground surface. Lava or
magma in contact with other
rock causes Contact
Metamorphism.
• Hornfels is a common contact
metamorphic rock.
CONTACT
Contact metamorphism
Contact
metamorphism
Contact metamorphism
along a narrow (approx. 1
meter wide) diabase dike in
the Deep River Basin of
North Carolina. Diabase
weathers tan. Contact
metamorphic aureole rocks
(hornfels) are gray. Host
rocks are red siltstones
Metamorfisme Rantau
• Pressure
• Burial Pressure. Pressure increases with
depth due to the weight of the overlying
rocks. A cubic foot of granite weighs 167.9
pounds. Increase of pressure and
temperature with depth causes Regional
Metamorphism. Regional metamorphism
occurs at depths of 5 - 40 km.
• Tectonic pressures associated with
convergent plate boundaries and
continental collision also cause Regional
Metamorphism.
• Pressure along fault zones causes
Dynamic Metamorphism, the crushing and
ductile flow of rock. Rocks formed along
fault zones are called mylonites
REGIONAL
Continental collision
SUBDUCTION
3 Chemical Fluids
• In some metamorphic settings, new
materials are introduced by the action of
hydrothermal solutions (hot water with
dissolved ions). Many metallic ore deposits
form in this way.
• Hydrothermal solutions associated with
magma bodies
• Black smokers - Sea water percolates
through newly formed oceanic crust,
dissolving out metallic sulfide minerals. The
hot sea water rises along fractures and
pours from vents in the seafloor as black
clouds of dark mineral-rich water. Sulfide
minerals (such as pyrite, sphalerite, and
galena) and copper precipitate when the hot
water comes in contact with cold sea water
HYDROTHERMAL
How do rocks change?
Metamorphism causes changes in:
1
Texture (definition: shape, size
and orientation of
mineral
grains in the rocks)
2
Mineralogy (chemical
composition)
STRESS
FOLIATION
FOLIATION
STRESS
FOLIATED
Foliasi
Texture
• The processes of compaction and
recrystallization change the
texture of rocks (shape, size and
orientation) during
metamorphism.
• Compaction
The grains move closer
together.
The rock becomes more
dense.
Porosity is reduced. Note:
this is engineering parameter
• Example: clay to shale to slate
Recrystallization
Growth of new crystals. No changes
in overall chemistry. New crystals
grow from the minerals already
present. A preferred orientation of
minerals commonly develops under
applied pressure. Platy or sheet-like
minerals such as muscovite and
biotite become oriented
perpendicular to the direction of
force. This preferred orientation is
called foliation.
Metamorphic
Textures
Foliation is a broad term referring to the
alignment of sheet-like minerals. Types of
foliation:
• Schistosity - alignment of large mica flakes, as
in a mica schist derived from the
metamorphism of shale.
• Slaty cleavage - alignment of very fine-grained
micas, as in a slate derived from the
metamorphism of shale.
• Phyllitic structure - alignment of fine-grained
micas, as in a phyllite.
• Gneissic banding - segregation of light and
dark minerals into distinct layers in the rock,
as in a gneiss
Lineation
refers to the alignment of
elongated, rod-like minerals
such as amphibole, pyroxene,
tourmaline, kyanite, etc.
Lineation is a texture commonly
seen in the metamorphic rock
amphibolite derived from the
metamorphism of basalt
Non-foliated or granular
metamorphic rocks
• are those which are composed
of equidimensional grains such
as quartz or calcite. There is no
preferred orientation. The
grains form a mosaic.
Examples: quartzite derived
from the metamorphism of
quartz sandstone, and marble
derived from the metamorphism
of limestone or dolostone.
• Note: Not all quartzites and
marbles are pure. Some contain
impurities that were originally
mud interlayered with or mixed
with the original quartz sand or
lime mud. These clay impurities
metamorphose to layers of
micas or other minerals, which
may give marble (in particular) a
banded, gneissic appearance, or
which may give a slight foliation
to some quartzites
Foliated metamorphic
rocks
As shale is subjected to
increasing grade of
metamorphism (increasing
temperatures and pressures), it
undergoes successive changes
in texture associated with an
increase in the size of the mica
grains
Slate
very fine grained rock.
Resembles shale. Has slaty
cleavage which may be at an
angle to the original bedding.
Relict bedding may be seen on
cleavage planes. Often dark gray
in color. "Rings" when you strike
it. (Unlike shale, which makes a
dull sound. Temperature about
200 degrees C; Depth of burial
about 10 km.
slate
Phyllite
fine-grained metamorphic rock.
Has a frosted sheen, resembling
frosted eye shadow. This is no
coincidence. Cosmetics
commonly contain ground up
muscovite (ground to a size
similar to that occurring
naturally in phyllite.)
phyllite
Schist
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metamorphic rock containing abundant
obvious micas, several millimeters
across. Several types of schist may be
recognized, based on minerals which
may be present:
mica schist
garnet schist
chlorite schist
kyanite schist
talc schist
schist
Gneiss
(pronounced "nice") - a banded
or striped rock with alternating
layers of dark and light
minerals. The dark layers
commonly contain biotite, and
the light layers commonly
contain quartz and feldspar
gneiss
gneiss
Migmatite
a very high grade metamorphic
rock that has been subjected to
such high temperatures that it has
partially melted. It is intermediate
between the metamorphic and the
igneous rocks. Look for swirled
banding. The light colored
minerals have undergone melting
and flow. The dark colored
minerals have been contorted by
flow. Example - the Lithonia
Gneiss in the area southeast of
Atlanta
migmatite
non-foliated (and weakly foliated)
metamorphic rocks
• Marble - fizzes in acid because
its dominant minerals is calcite
(or dolomite). The parent rock
is limestone (or dolostone).
Marmar (Marble)
Quartzite/kuarzit
interlocking grains of quartz.
Scratches glass. The rock
fractures through the grains
(rather than between the grains
as it does in sandstone). The
parent rock is quartz sandstone
Hardest rock known
UCS
quartzite
Others
• Metagraywacke metamorphosed graywacke or
"dirty sandstone".
• Metaconglomerate and
stretched pebble
metaconglomerate - the parent
rock is conglomerate. The clasts
are fairly easily recognized. May
be more difficult to recognize if
the clasts have been stretched
Hornfels
A fine-grained, tough, dense,
hard, massive rock. Usually (but
not always) dark in color. Finer
grained than basalt, which it
may superficially resemble. This
rock forms through contact
metamorphism. The parent rock
is commonly siltstone or basalt,
but may be other types of rock
Serpentinite
A dark green, dense, tough,
massive, hard rack. May contain
veins of asbestos. The parent
rock is peridotite, an ultramafic
rock
ultramafic: lack/low amount of
SiO2, Fe, Mg (bandingkan dgn
jadual pengelasan batuan
igneus)
serpentine
Soapstone
(sometimes called steatite) - a soft,
easily carved rock with a slippery
feel because it contains talc and
chlorite. The parent rock is
peridotite (ultramafic), probably
with more water associated with it
than in the formation of
serpentinite. Example - Soapstone
Ridge southeast of Atlanta
Metabasalt
(sometimes called greenstone if
massive and green, or
greenschist if foliated and
green) - the green color comes
from chlorite (soft and bluish
green) and epidote (pea green).
The parent rock is basalt. The
grade of metamorphism is LOW
Amphibolite
Abundant amphibole is present;
may be lineated. Usually black.
The parent rock is basalt. The
grade of metamorphism is
HIGH. Has been subjected to
higher temperatures and
pressures than metabasalt,
greenstone, or greenschist.
Mylonite
A dynamic metamorphic rock
which forms along fault zones
mylonite
Mylonite along the Linville Falls Fault, Linville Falls,
NC. Relatively undeformed conglomeratic quartzite
lies above the layered mylonite zone
Mineral changes in
metamorphic rocks
Recrystallization - rearrangement of
crystal structure of existing minerals.
Commonly many small crystals
merge to form larger crystals, such
as the clay in shale becoming micas
in slate, phyllite, and schist. Note the
chemical compositions of clay and
muscovite.
• Also, fine-grained calcite in limestone
recrystallizes to the coarse-grained
calcite mosaic in marble
Formation of new minerals
there are a number of
metamorphic minerals which
form during metamorphism and
are found exclusively (or almost
exclusively) in metamorphic
rocks:
• Garnet - dark red
dodecahedrons (12 sides)
• Staurolite - brown lozengeshaped minerals, commonly
twinned to form "fairy crosses".
State mineral of Georgia
garnet
Kegunaan?
Kyanite
sky blue bladed minerals with
differential hardness. Scratch
lengthwise with a knife or nail,
but not sideways
kyanite
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Chlorite - dark bluish green, soft. Fe, Mg
Talc - white or pale green and soft.
Graphite - metamorphosed carbon
Tourmaline - commonly black. Forms
elongated crystals with a rounded
triangular cross-section. Can see at
Stone Mountain.
• Asbestos - fibrous mineral. Commonly
light greenish. Occurs in veins (seems
to fill a crack) with the fibers oriented
perpendicular to the edged of the vein.
Associated with lung diseases.
Mesothelioma and asbestosis. Found in
serpentinite. "Serpent rock" name due
to snake-like veins of asbestos.
• Micas - muscovite (silvery), biotite (dark
brown), phlogopite (light brown)
Metamorphic index minerals
• Batuan metamorfik boleh digunakan
sebagai tanda aras suhu dan tekanan
dalam bumi
• In regional metamorphic terranes, the
temperature and pressure regime is
indicated by the distribution of
metamorphic minerals across a large area.
Low metamorphic grade (low temperatures
and pressures) - about 200 degrees C
Slate and phyllite
• chlorite
• muscovite
• biotite
Intermediate metamorphic grade
• Schist
• garnet
• staurolite
KOMPOSISI KIMIA?
High metamorphic grade - 800
degrees C (verging on melting)
Gneiss and migmatite
• sillimanite
• Know which minerals are the
metamorphic index minerals.
Know which ones are
characteristic of low,
intermediate, and high
metamorphic grades
FACIES GRADE
FACIES
pandangan
• Jurutera bahan banyak
menggunakan bahan ini untuk
membuat bahan baru => bahan
termaju (advanced materials),
composite materials,
nanomaterials
• Keadaan makmal cuba
disimulasikan seperti yang
ditemui di dalam bumi
sistem berbeza: open vs closed
REGIONAL
Mineral yg terdapat pada
zon metamorfik
foliation
Slate
schist
gneiss texture
Granular texture as in
quartzite
Rumus
Changes that occur in the
transformation to become
metamorphic rocks
ENGINEERING
PROPERTIES
1.
2.
3.
4.
POROSITY
KEKUATAN EKAPAKSI (UCS)
PERMEABILITY
ABRASIVENESS
HOW
WHERE
CONTACT
METAMORFISME
JENIS
REGIONAL/
DYNAMIC
PREEXISTING
ROCKS
T, P, CHEMICAL
FLUIDS
BATUAN
METAMORFIK
HOW
WHERE
JENIS BATUAN
& CIRI KEJURUTERAAN
LINEATION
TEXTURE
FOLIATION
CHANGES
MINERALOGY
NONFOLIATED
PHASE DIAGRAM FOR WATER
NEXT LECTURE
• MASA GEOLOGI