E T R O L O U N A P [TGS 7404 ] Dr. Hill. Gendoet Hartono Semester 7, 20 1 7 - 2018 2 SKS teori G I B A G I T U A N
PENDAHULUAN 1X
Berisi tentang latarbelakang, bumi, batuan beku dan
batuan gunung api, dan kedudukan di bidang geologi
TATAAN TEKTONIK 2X
Berisi tentang tektonik global, regim tektonik, dan
peranannya dalam magmatisme dan volkanisme
GENERASI MAGMA 2X
Berisi tentang magmatisme, diagram fase
KLASIFIKASI 2X
Klasifikasi magma atau afinitas magma
Rock Forming Mineral 1X
Kimia Mineral Pembentuk Batuan 1X
Petrologi Batuan Intrusi Dangkal 2X
Petrologi Batuan Ekstrusi 2X
Alterasi Batuan Gunung Api 1X
The mineral olivine is a magnesium iron silicate with the formula (Mg2+,
Fe2+)2SiO4. Thus it is a type of nesosilicate or orthosilicate. It is a common
mineral in the Earth's subsurface but weathers quickly on the surface.
The ratio of magnesium and iron varies between the two endmembers of the
solid solution series: forsterite (Mg-endmember: Mg2SiO4) and fayalite (Fe-
endmember: Fe2SiO4). Compositions of olivine are commonly expressed as
molar percentages of forsterite (Fo) and fayalite (Fa) (e.g., Fo70Fa30). Forsterite
has an unusually high melting temperature at atmospheric pressure, almost
1,900 °C (3,450 °F), but the melting temperature of fayalite is much lower
(about 1,200 °C [2,190 °F]). The melting temperature varies smoothly between
the two endmembers, as do other properties. Olivine incorporates only minor
amounts of elements other than oxygen, silicon, magnesium and iron.
Manganese and nickel commonly are the additional elements present in
highest concentrations.
Olivine gives its name to the group of minerals with a related structure (the
olivine group) which includes tephroite (Mn2SiO4), monticellite (CaMgSiO4)
and kirschsteinite (CaFeSiO4).
OLIVINE END-MEMBERS
• Forsterite Mg2SiO4
• Fayalite Fe2SiO4
•Tephroite Mn2SiO4
• Liebenbergite Ni2SiO4
•Co-olivine Co2SiO4
•Ca-olivine Ca2SiO4
•Monticellite CaMgSiO4
•Kirschsteinite CaFeSiO4
•Glaucochroite CaMnSiO4
OLIVINE OCCURRENCES
• Forsterite - Fayalite
Fo90 Olivine is major mineral of upper mantle
Minor phase in basalt and gabbro
Fayalite is secondary in silicic volcanics
• Monticellite accessory in mantle nudules
• Tephroite and glaucochroite
silicic volcanics and Mn skarns
• Liebenbergite secondary in Ni deposits
Fe Mg
Si
fayalite forsterite
enstatite ferrosilite
Pyroxene solid solution MgSiO3 – FeSiO3
Olivine solid solution Mg2SiO4 – Fe2SiO4
Fe Mg
forsteritefayalite
INOSILICATES (CHAIN)
• XY(Si2O6) in Pyroxenes, WX2Y5Si8O22(OH,F)2 in Amphiboles
• Single and double silicon tetrahedra chains respectively
• Typically monoclinic and orthorhombic symmetry
• Single chains (Pyroxenes) develop ~90° cleavage
• Double chains (Amphiboles) develop 120 ° cleavage
Amphibole StructurePyroxene Structure
Orthorhombic Pyroxenes (Orthopyroxenes - Opx)These consist of a range of compositions between Enstatite - MgSiO3 and Ferrosilite - FeSiO3
Monoclinic Pyroxenes (Clinopyroxenes - Cpx)The Diopside- Hedenbergite series - Diopside (CaMgSi2O6) - Ferrohedenbergite (CaFeSi2O6)
Augite - (Ca,Na)(Mg,Fe,Al)(Si,Al)2O6 is closely related to the Diopside - Hedenbergite series with addition of Al and minor Na substitution
There is complete Mg-Fe solid solution between Diopside and (Ferro)Hedenbergite
There is also a complete Mg-Fe substitution and small amounts of Ca substitution into the Orthopyroxene solid solution series. Old name Hypersthene
Pigeonite is a high Temperature clinopyroxene
SOLID IMMISCIBILITY
Pigeonite is only found in hot volcanic and shallow intrusive igneous rocks, or as exsolution lamellae
Pigeonite crystallizes in the monoclinic system, as does Augite, and a miscibility gap exists between the two minerals.
Cpx
At lower temperatures, Pigeonite is unstable relative to Augite plus Orthopyroxene.
Pigeonite => Augite + Opx
Pigeonite (Ca,Mg,Fe)(Mg,Fe)Si2O6
Augite (Ca,Na)(Mg,Fe,Al)(Si,Al)2O6
Opx
COMMON TYPES OF AMPHIBOLES
COMMON PHYLLOSILICATES
Antigorite
ChrysotileKaolinite
Talc
Pyrophyllite
Muscovite
Lepidolite
BiotiteChlorite
Prehnite
Tectosilicates (Framework)
3-D framework of linked silicon tetrahedra
Variable physical properties and symmetries depending on linkage of framework groupings
FELDSPAR GROUPMost abundant minerals, by mass or volume, in the crust
Compositionsfor Feldspars are commonly described in terms of mole percents of the end membercomponents (e.g. Or85Ab15, An54Ab39)
Microcline
Anorthite
XAl(Al,Si)3O8
Notice that Albite is an end member of both the Plagioclase and K-Spar (Alkali Feldspar) groups
Albite
ALKALI FELDSPARS
Perthite (albite exsolution in microcline)
Triclinic K-spar “Microcline”
Sanidine
Albite
At low temperatures solid solution (ss) is unstable, ss exsolves to Albite + Microcline. We say the two phases are immiscible