Batuan Beku - Pendidikan Geografi UMS

PETROLOGY
1. Description of rocks
2. Classification of rocks
3. Theories on how these rocks formed
Crystallize from molten
material
• Magma - below the
Earth's surface
• Lava - erupts onto the
Earth's surface through
a volcano or crack
(fissure)
Lava cools more
quickly because it is on
the surface.
Cooling Rates
• Cooling rates influence
the texture if the
igneous rock:
• Quick cooling = fine
grains
• Slow cooling = coarse
grains
EKTRUSIF/VULCONIK (Batuan Beku Luar)
1. Terbentuk di permukaan bumi.
2. Pembentukan mineral berjalan cepat
3. Kristalisasi tidak terjadi/kurang
sempurna
4. Ukuran mineral tidak dapat dilihat
dengan mata.
5. Tekstur halus
INTRUSIF/PLUTONIK (Batuan Beku Dalam)
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2.
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4.
Terbentuk jauh di dalam bumi.
Pembentukan mineral berjalan lambat
Kristalisasi sempurna
Ukuran mineral dapat dilihat dengan
mata.
5. Tekstur kasar
Igneous textures
Glassy =
instantaneous
cooling
Obsidian
(volcanic glass)
• Aphanitic - fine
grain size (< 1
mm); result of
quick cooling
Basalt
Rhyolite
Andesite
Phaneritic coarse grain
size; visible
grains (1-10
mm); result of
slow cooling
• Granite
• Diorite
• Gabbro
Vesicular - contains tiny
holes called vesicles
which formed due to
gas bubbles in the
lava or magma. Very
porous. May resemble
a sponge. Commonly
low density; may float
on water.
Composition of Igneous Rocks
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4.
Felsic (granitic or Sialic )
Intermediate (or andesitic)
Mafic (or basaltic)
Ultramafic
Felsic (granitic or Sialic )
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•
•
•
•
Dominated by silicon and aluminum (SiAl)
Usually light in color
Characteristic of continental crust
Rock types include: Granite, Riolite
Accecories mineral :potassium feldspar
(generally pink or white) , Na-plagioclase feldspar
(generally white) , quartz (generally gray or
colorless) , biotite
Intermediate (or andesitic)
Intermediate in composition between sialic
and mafic
Rock types include:
Andesite (aphanitic)
Diorite (phaneritic)
Accecories mineral :
plagioclase feldspar, amphibole, pyroxene,
biotite, quartz
Mafic (or basaltic)
• Contains abundant ferromagnesian
minerals (magnesium and iron silicates)
• Usually dark in color (dark gray to black)
• Characteristic of Earth's oceanic crust,
Hawaiian volcanoes
• Forms a runny (low viscosity) lava
• Rock types include: Basalt, Gabbro
Ultramafic
• Almost entirely magnesium and iron silicates
(ferromagnesian minerals)
• Rock types include:
Peridotite (phaneritic)
– dominated by olivine - the birthstone is Peridot, which
gives its name to Peridotite
• Minerals commonly present include:
Olivine is dominant. (Olivine is olive green).
may have minor amounts of pyroxene and Caplagioclase
Order of crystallization
by Dr. N.L. Bowen
MAFIC
GABBRO
This is a mafic
igneous
intrusive rock.
DIORITE
This speckled
coarse-grained
specimen is an
intermediate
composition
igneous
intrusive rock.
GRANITE – This is a felsic intrusive rock.
BASALT
This typically
dark, mafic to
ultramafic
volcanic rock is
apparently
featureless.
The presence
of olivine
suggests it is
ultramafic.
RHYOLITE
The lighter
colour is
indicative of the
felsic
composition of
this extrusive
rock.
Kelompok Batuan Beku
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Rhyolit – Granit
Trachit- Syenit
Dasit-Kwarsa Dasit
Andesit-Diorit
Gabro-Basalt