1. petrologi [TGS7208] 2 SKS teori 1 SKS praktikum Semester 2, 2017-2018
by:
hill. gendoet hartono

2. UTS UAS Siklus Batuan, Kontrak Kuliah, Kelulusan, & Praktikum
Magma, Diferensiasi, Viskositas, Gas dan Komposisi
Batuan Beku, Intrusi Dalam & Karakteristiknya
Batuan Gunung Api, Intrusi Dangkal & Karakteristiknya
Batuan Gunung Api, Lelehan, Letusan & Karakternya
Klasifikasi Batuan Beku & Gunung Api
Batuan Alterasi
UTS
Batuan Sedimen, Jenis & Proses Pembentukan
Batuan Sedimen Silisiklastika
Batuan Sedimen Karbonat
Klasifikasi Batuan Sedimen
Batuan Metamorf, Jenis & Proses Pembentukan
Batuan Metamorf Derajat Rendah, Menengah & Tinggi
Klasifikasi Batuan Metamorf
UAS

3. mula jadi MAGMA

4. mag·ma
ˈmaɡmə’
noun
noun: magma; plural noun: magmata; plural noun: magmas
hot fluid or semifluid material below or within the earth's crust from which lava and other igneous rock is formed by cooling.
Dictionary

5. Magma (from Ancient Greek μάγμα (mágma) meaning "thick unguent") is a mixture of molten or semi-molten rock, volatiles and solids that is found beneath the surface of the Earth, and is expected to exist on other terrestrial planets and some natural satellites. Besides molten rock, magma may also contain suspended crystals, dissolved gas and sometimes gas bubbles. Magma often collects in magma chambers that may feed a volcano or solidify underground to form an intrusion. Magma is capable of intruding into adjacent rocks (forming igneous dikes and sills), extrusion onto the surface as lava, and explosive ejection as tephra, or fragmented rock, to form pyroclastic rock.
From Wikipedia, the free encyclopedia

7. Origin of Magma Where does the heat come from that melts rocks?
Formation of Earth
Heat from the decay of radioactive elements

8. Factors that Affect Magma Formation
Temperature
Increases with depth
Pressure
Water Content
Decreases melting point
Mineral Composition
Different minerals, different melting points

9. Sources of Magma

10. Origin of Magmas
MORBs
Subduction
Continental

11. Karakteristik Magma
Slushy Mix of molten rock, gases, and mineral crystals
Common Elements
Oxygen (O)
Silicon (Si)
Aluminum (Al)
Iron (Fe)
Magnesium (Mg)
Calcium (Ca)
Potassium (K)
Sodium (Na)
Compounds in Magma
Silica ( Si02)
Most abundant
Greatest effect on Magma Characteristics
Effects melting temp
Viscosity of Magma
Types of Magma
Based on amount of Silica
Basaltic
Andesitic
Rhyolitic

12. Types of magma are determined by chemical composition of the magma
Types of magma are determined by chemical composition of the magma. Three general types are recognized:
Basaltic magma --  SiO2 45-55 wt%, high in Fe, Mg, Ca, low in K, Na
Andesitic magma --  SiO2 55-65 wt%, intermediate. in Fe, Mg, Ca, Na, K
Rhyolitic magma --  SiO2 65-75%, low in Fe, Mg, Ca, high in K, Na

13. DENSITY
Density controlled by magma composition: FeO wt% most important.
In general, basalts are richer in Fe, Ca, and Ti than rhyolites; rhyolites are richer in Na, Al, and Si than basalts:
Basalt magma: 2.65 to 2.80 gm/cm3
Andesite magma: 2.45 to 2.50 gm/cm3
Rhyolite magma: 2.18 to 2.25 gm/cm3
Density is also controlled by Temperature and Pressure.
Higher Temperatures cause melts to Expand ==>> Lower Density
Higher Pressures cause the melts to Compress == >> Higher Density

14. VOLATILES H2O most abundant volatile in most magmas
CO2 next most abundant volatile
In general, Basalt magmas are DRY, i.e. H2O < 0.5 wt%
MORB = 0.25% H2O
Hawaiian Tholeiite = 0.5% H2O
Alkali Olivine Basalt = 0.9% H2O
Andesites, Rhyolites, Granites: Higher Water Contents
Paricutin Andesite = 2.2% H2O at 1100oC
Granites/Rhyolites wide range H2O: 0.5% to 7% H2O by weight.
Water lowers viscosity: OH- ions act as Network Modifers, substitute for O2 in tetrahedra.
Water lowers solidus temperature: Effect greater at higher pressures

15. VISCOSITY
Viscosity is the resistance to flow (opposite of fluidity).  Viscosity depends on primarily on the composition of the magma, and temperature.
Viscosity decreases with increasing temperature and high H2O, CO2.
Some Natural Viscosities In Poise {= gm/cm-sec}
H2O at 20oC 0.01 poise
Glycerin 15 poise
Erupting Hawaiian Basalt 3 x o-1200oC
Rhyolite Magma 108 to oC
Asthenosphere oC

16. Higher SiO2 (silica) content magmas have higher viscosity than lower SiO2 content magmas (viscosity increases with increasing SiO2 concentration in the magma).
Lower temperature magmas have higher viscosity than higher temperature magmas (viscosity decreases with increasing temperature of the magma).
Thus, basaltic magmas tend to be fairly fluid (low viscosity), but their viscosity is still 10,000 to 100,000 times more viscous than water.  Rhyolitic magmas tend to have even higher viscosity, ranging between 1 million and 100 million times more viscous than water.  (Note that solids, even though they appear solid have a viscosity, but it is very high, measured as trillions time the viscosity of water).  Viscosity is an important property in determining the eruptive behavior of magmas.
Viscosity has a control on magma flow rates, volcano morphology, rates of gas escape, ratesof convection, rates of crystal settling or flotation, rates of diffusion and crystal growth.

17. FLUIDITY OF MAGMA
Fluidity or Viscosity of magma depends on content (%) of Silica
Silica Rich
known as Acidic magma
More viscous, so do not spreads and piles up at one place
Silica poor
-Known as Basic magma
-Less viscous, moves faster and occupies larger area
However, the viscosity of magma is considerably influenced by
temperature too. When temperature is less-more viscous and when
high temperature- less viscous.

18. Pahoehoe aa

19. Gases in Magmas
At depth in the Earth nearly all magmas contain gas dissolved in the liquid, but the gas forms a separate vapor phase when pressure is decreased as magma rises toward the surface.  This is similar to carbonated beverages which are bottled at high pressure. The high pressure keeps the gas in solution in the liquid, but when pressure is decreased, like when you open the can or bottle, the gas comes out of solution and forms a separate gas phase that you see as bubbles.   Gas gives magmas their explosive character, because volume of gas expands as pressure is reduced.  The composition of the gases in magma are:
Mostly H2O (water vapor) with some CO2 (carbon dioxide)
Minor amounts of Sulfur, Chlorine, and Fluorine gases
The amount of gas in a magma is also related to the chemical composition of the magma.   Rhyolitic  magmas usually have higher dissolved gas contents than basaltic  magmas.

20. Ringkasan Magma Type Solidified Rock Chemical Composition Temperature
Viscosity
Gas Content
Basaltic
Basalt
45-55 SiO2 %, high in Fe, Mg, Ca, low in K, Na
 oC
 PaS
Low
Andesitic
Andesite
55-65 SiO2 %, intermediate in Fe, Mg, Ca, Na, K
 oC
103 - 105 PaS
Intermediate
Rhyolitic
Rhyolite
65-75 SiO2 %, low in Fe, Mg, Ca, high in K, Na.
 oC
105 - 109 PaS
High

21. Igneous rocks are classified as felsic, mafic, intermediate, and ultramafic, depending upon their mineral compositions.
Felsic rocks such as granite are light- colored, have high silica contents, and contain quartz and feldspars.
Mafic rocks such as gabbro are dark-colored, have lower silica contents, and are rich in iron and magnesium.
Intermediate rocks have moderate silica levels.
Ultramafic rocks have low silica contents and very high levels of iron and magnesium.
Igneous groups can be further identified by crystal size and texture.

22. See You….Soon