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ROCK FORMING MINERALS
Okki Verdiansyah, M.T.
KULIAH MINERAL OPTIK STTNAS – TGS SEMESTER GANJIL- 2015
1) Rock forming minerals (3x) 2) Secondary / Alteration minerals (1x) 3) Non silicates and opaque minerals (1x) 4) Diskusi dan presentasi mahasiswa (1x)
IGNEOUS ROCKS
Bowen, N. L., 1922, The reaction principle in petrogenesis, The Journal of Geology, Vol. 30, No. 3, pp. 177-198
Norman Levi Bowen (1887 – 1956) paper yg dibuat :
The later stages of the evolution of igneous rocks (1915)
The problem of the anorthosites (1917), Crystallization differentiation in igneous magmas
(1919), Diffusion in silicate melts (1921), Genetic features of alnoitic rocks (1922), The reaction principle in petrogenesis (1922), The behavior of inclusions in magmas (1922), The origin of ultrabasic and related rocks
(1927) The evolution of igneous rocks (1928) [buku]
Igneous Rock : Minerals
• Olivine – Forsterite
– Fayalite
• Pyroxene – Clino : Augite
– Ortho : Hypersthene
• Hornblende
• Biotite
• K-Feldspar – Orthoclase, Microcline, Sanidine
• Plagioclase
• Muscovite
• Quartz
• Magnetite
• Ilmenite
Fungsi Mineral Optik
Identifikasi mineral dengan baik, berupa - Nama mineral
- Tekstur internal kristal (zoning, inklusi, eksolusi)
- Tekstur antar kristal mineral (ofitik, interloking, mozaik, dan lainnya)
- Tekstur diagenesa (alterasi)
Untuk kegunaan lebih lanjut : - Petrogenesis
OCEANIC BASALT VOLCANO SEAMOUNT – INDIAN OCEAN Igneous Petrogenesis
1. Mid-ocean ridges
2. Continental rifts
3. Island Arcs
4. Active continental margins
5. Back-arc basins
6. Ocean Islands
7. Intraplate hotspot activity, carbonatites, or kimberlites
Tholeiites Alkali Basalts
Mid‐ocean ridges, oceanic islands, subduction
zonesOcean islands, subduction zones
Shallower melting (25% melting at <30 km =
tholeiite)
Deeper melting (25% melting at 60 km =
alkaline basalt)
Greater % partial melting ( 30% melting at 60 km =
tholeiite)
Lesser % partial melting (20% melting at 60
km = alkaline basalt)
Fine-grained Coarse
No olivine Olivine common
Quartz, interstitial glass common No quartz; interstitial glass rare
Clinopyroxene (augite, pigeonite) Titaniferous augite (reddish)
Ca-poor orthopyroxene (hypersthene) No orthopyroxene
No alkali feldspar Interstitial alkali feldspar or feldspathoid
Olivine rare, unzoned or orthopyroxene rims Olivine common, zoned
Olivine < plag < augite Olivine < augit < plagio
Orthopyroxene uncommon Orthopyroxene absent
Early plagioclase common Plagioclase less common, appears later
Clinopyroxene = pale brown augiteClinopyroxene = titaniferous augite with
reddish rims
Formation
Groundmass
Phenocrysts
Metamorph
Concept of Index Minerals
Sediment
Sedimentary Rock : Minerals
Feldspar
Quartz
Mafic minerals (pyroxene, amphibole)
Carbonates
Calcite – Dolomite
Fossils
Oxide
Limonite
Clay minerals
Kaolinite, illite, smectite
Lithic (Igneous, Sediment, Metamorph)
Sedimentary rocks
component :
Grains
Matrix
Cement
Pores
Materi RFM Kuliah MO 2015
Olivine
Pyroxene
Hornblende
Biotite
Muscovite
K-Feldspar
Plagioclase
Quartz
Carbonates
Refraction Index : (Indeks Bias)
http://www.uwgb.edu/dutchs/petrology/mintable1.htm
Refraction Index : (Indeks Bias)
CRYSTAL SHAPE
Euhedral
(Demange, M., 2012)
Olivine
forsterite fayalite.
Forsterite – fayalite phase diagram, (Bowen and schrainer, 1932)
Olivine
webmineral.com
Olivine ((Mg,Fe)2Si04) Forsterite (Fo)
Mg2 Si04
Fayalite (Fa)
Fe2 Si04
Sifat Optik Forsterite (Fo) Fayalite (Fa)
Rumus Kimia Mg2 Si04 Fe2 Si04
Sistem kristal
Indeks refraksi
colour (warna) colourless pale yelow
Habit (bentuk)
cleavage (belahan)
fracture (retakan)imperfect, none moderate, none
Pleochroisme (pleokroik) none pale yellow - orange yellow
Relief moderate very high
Birefringe (biasrangkap) δ 0.0330-0.0420 0.0420-0.0510
Int. colour max, (warna terang maks)
Extinction (pemadaman)
Orientation / orientasi X = b; Y = c; Z = a. X = b; Y = c; Z = a
Optic sign (tanda optik) Biaxial (+) Biaxial (-)
2V(Calc)=56-84, 2V(Meas)=74-90 2V(Calc)=54-66, 2V(Meas)=74-47
Ortorombik
nα=1.636 - 1.827
nβ=1.651 - 1.869
nγ=1.669 - 1.879
Equant or slightly elongated prismatic crystals
Tabel perbandingan sifat optik mineral Olivin
Olivine, phenocryst in an Iceland basalt
Olivine ((Mg,Fe)2Si04)
Olivine ((Mg,Fe)2Si04)
c
b
100
Forsterite 84, 2V=90.
Pyroxene
Sifat Optik Ortopiroksen Klinopiroksen
Rumus Kimia (Mg, Fe) 2 Si 2 O 6 (Ca, Mg, Fe(Na, Al, Fe*)) 2 Si 2 O 6
Sistem kristal Ortorombik Monoklinik
Indeks refraksi n: 1.657 - 1.788n: 1.665 - 1.772,
n aegirin : 1.665 -1.826
colour (warna)colourless (pale brown, pale
green, pinkish)
colourless - greenish, purplish
brown
Habit (bentuk)
cleavage (belahan)
fracture (retakan)
Pleochroisme (pleokroik)Pale colored with greenish to
pinkish pleochroism-
Relief moderate moderate-very high
Birefringe (biasrangkap) δ 0.008-0.022 0.023-0.031, 0.034 - 0.052
Int. colour max, (warna terang maks)
Extinction (pemadaman) Parallel, symetry Incline
Orientation / orientasi
Optic sign (tanda optik) Biaxial (+)/(-) Biaxial (+)
2Vz : 25 - 70
slightly elongated, prismatic crystals
Two cleavage planes : 87 - 93 at 001, 1 cleaveage at 010,100
Pembeda utama Ortopiroksen dan Klinopiroksen
1) Sudut pemadaman
2) Pleokroisme [biasa hadir pada enstatit]
3) Ortopiroksen mempunyai birefringe (orde 1) lebih rendah dari pada klinopiroksen (orde 2 – 3)
4) Ortopiroksen tidak mempunyai kembaran, seperti klinopiroksen (pigeonit selalu ada kembaran)
Ortho-Pyroxene
Sifat Optik Enstatite Hypersthene
Rumus Kimia MgSiO3 (Mg,Fe)SiO3
Sistem kristal
Indeks refraksi
nα = 1.650 - 1.668
nβ = 1.652 - 1.673
nγ = 1.659 - 1.679
nα = 1.669 - 1.755
nβ = 1.674 - 1.763
nγ = 1.680 - 1.773
colour (warna)colorless, higher Fe contents
correspond to darker colors
colourless (pale brown, pale
green, pinkish)
Habit (bentuk)
cleavage (belahan)
fracture (retakan)
Pleochroisme (pleokroik)
Relief
Birefringe (biasrangkap) δ 0.009 - 0.011 0.011 - 0.018
Int. colour max, (warna terang maks)
Extinction (pemadaman)
Orientation / orientasi
Optic sign (tanda optik) Biaxial (+) Biaxial (-)
2V:M: 54° to 90°, C: 58° to 86° 2V:M: 70° to 90°, C: 86°
Longitudinal sections will show parallel extinction. Basal sections
will show symmetrical extinction.
prismatic crystals
Ortorombik
moderate - high
Two cleavage planes : 87 - 93 at 001, 1 cleaveage at 010,100
Pale colored with greenish to pinkish pleochroism
Tabel perbandingan sifat optik ortopiroksen
Orthopyroxene - Sample SIC -5. Orthopyroxene seen in the center. Note plagioclase (left of orthopyroxene) with typical twinning. Image by Andrea Gohl. (http://www.science.smith.edu/geosciences)
Opx Opx
A micrograph of an enstatite crystal taken from an ultramatic rock. The thin lamellae of a calcium-rich species, probably pigeonite, have separated from the bronzite; the gray coloration of the host rock betrays its very low calcium content (magnified about 40× [http://www.britannica.com/science/pyroxene
Hypersthene
Sifat Optik Augite Diopside
Rumus Kimia(Ca,Na)(Mg,Fe2+,Al,Fe3+,Ti)[(Si,Al)2O6
]CaMgSi2O6
Sistem kristal Monoklin Monoklin
Indeks refraksi
α = 1.680 - 1.735
nβ = 1.684 - 1.741
nγ = 1.706 - 1.774
nα = 1.663 - 1.699
nβ = 1.671 - 1.705
nγ = 1.693 - 1.728
colour (warna)
X= pale green, pa le brown, green,
greenish yel low
Y= pale brown, pa le yel low-green, violet
Z= pale green, grayish green, violet
Habit (bentuk) prismatic crystals
cleavage (belahan)
fracture (retakan)
Two cleavage planes : 87 - 93 at 001, 1
cleaveage at 010,100
Pleochroisme (pleokroik) Visible
Relief high high
Birefringe (biasrangkap) δ 0.026 - 0.039 δ = 0.030
Int. colour max, (warna terang maks)
Extinction (pemadaman) Z : c = 35°-48°
Orientation / orientasi
Optic sign (tanda optik) Biaxial (+) Biaxial (+)2V:Measured: 40° to 52°, Calculated: 48° to
68°
2V:Measured: 58° to 63°,
Calculated: 56° to 64°
Modification by Verdiansyah, 2015
Tabel perbandingan sifat optik antara Augit dan Diopsid
Augite (Ca,Na)(Mg,Fe,Al)(Si,Al)2O6
Section c
(100) Section
(010) Section
c
a
b
Augite
Ortho – clinopyroxene intergrowth
Pyroxene
Amphibole
Hornblende
Amphiboles & Pyroxenes
Hornblende ((Na,K)0-1Ca2(Mg,Fe,Al)5 (Si,Al)8O22(OH)2)
Sifat Optik Ferro Hornblende Magnesio Hornblende
Rumus Kimia {Ca2}{Fe42+Al}(AlSi7O22)(OH)2 {Ca2}{Mg4Al}(AlSi7O22)(OH)2
Sistem kristal Monoklin Monoklin
Indeks refraksinα = 1.687 - 1.694
nβ = 1.700 - 1.707
nγ = 1.701 - 1.712
nα = 1.616 - 1.680
nβ = 1.626 - 1.695
nγ = 1.636 - 1.700
colour (warna)
Habit (bentuk)
cleavage (belahan)
fracture (retakan)
Pleochroisme (pleokroik)
strongly pleochroic :
Pleochroism (x): deep brown or pale greenish
brown.
Pleochroism (y): straw yellow or dark greenish
brown.
Pleochroism (z): yellow or bluish green.
strongly pleochroic :
x: l ight green, yellowish green, yellow,
greenish brown, or yellow
y: dark green, dark yellowish green,
brown. Pale, reddish brown, or
greenish yellow
Relief high Moderate
Birefringe (biasrangkap) δ δ = 0.014 ‐ 0.018 δ = 0.02
Int. colour max, (warna terang maks)
Extinction (pemadaman)
Orientation / orientasi
Optic sign (tanda optik)
2V:Measured: 12° to 76°, Calculated: 30° to 62°2V:Measured: 66° to 85°, Calculated: 58° to
88
prismatic crystals
Usually strongly coloured in green, yellow-green, blue-green and brown.
Two: perfect prismatic [110] at 124 degree
12 - 34
Biaxial (-)
Modification by Verdiansyah, 2015
Quiz Identifikasi piroksen dan olivin :
(Demange, M., 2012)
Sediment
Sedimentary Rock : Minerals
Feldspar
Quartz
Mafic minerals (pyroxene, amphibole)
Carbonates
Calcite – Dolomite
Fossils
Oxide
Limonite
Clay minerals
Kaolinite, illite, smectite
Lithic (Igneous, Sediment, Metamorph)
Sedimentary rocks
component :
Grains
Matrix
Cement
Pores
Ammonite. Polarised light micrograph of a thin section through a fossilised ammonite, a type of shelled mollusc that lived around 200 million years ago. Crystals of calcite and quartz have developed in the spiral cavity of the ammonite's shell. Magnification x6 at 4x5ins size. (http://fineartamerica.com/---)
CARBONATES
CARBONATES
Kalsit
Aragonite
Rodokrosit
Siderite
Magnesit
http://www.mindat.org/
Dolomit
Ankerit
Kalsit
Sifat Optik Calcite Aragonite Dolomite
Rumus Kimia CaCO3 CaCO3 CaMg(CO3)2
Sistem kristal Trigonal Orthorhombic Trigonal
Indeks refraksinω = 1.640 - 1.660
nε = 1.486
nα = 1.529 - 1.530
nβ = 1.680 - 1.682
nγ = 1.685 - 1.686
nω = 1.679 - 1.681
nε = 1.500 - 1.503
colour (warna) colourless colourless colourless
Habit (bentuk)usually rhombohedral crystals when
euhedral
Usually radiating or columnar
elongate grainsOften as rhombohedral crystals
cleavage (belahan)
fracture (retakan)Three: perfect rhombohedral [101] One: imperfect cleavage [010] Three: perfect rhombohedral [101]
Pleochroisme (pleokroik) - - -
Relief Negative, Low, Moderate, High Negative, Low, Moderate Negative, Low, Moderate, High
Birefringe (biasrangkap) δ 0.154 - 0.174 0.156 0.179 - 0.182
Int. colour max, (warna terang maks)
Extinction (pemadaman) Parallel
Orientation / orientasi
Optic sign (tanda optik) Uniaxial (-) Biaxial (-) Uniaxial (-)2V: Measured: 18° to 19°, Calculated: 16° to 18°
Modification by Verdiansyah, 2015
Tabel perbandingan sifat optik mineral karbonat
Dolomite (CaMg(CO3)2)
Large botryoid of aragonite (A) from a stalagmite from Madagascar. Dark area in botryoid (red double-pointed arrow) is due to extinction of vertical crystals in cross-polarized light. Termination of crystals in right side of A against smaller cluster at right (a) suggests that the smaller cluster grew first and blocked growth of A in that direction. Black areas (V) are void space; truncation of aragonite crystals (e.g., white arrow) suggests that some or much of that void space is the result of dissolution of aragonite.
Aragonite (CaCO3)
Calcite (CaCO3)
BATUAN KARBONAT
Koesoemadinata, 1981
From left to right: Halimeda, Penicillus, Udotea, Rhipocephalus.
Halimeda
GREEN ALGAE
Mizzia sp
RED ALGAE
A crustose coralline red algal
possible segmented red alga
Mazloviporidium sp. (syn. Cribroporidium, Contortoporidium)
FORAMINIFERA
calcareous uniserial benthic foraminifer in a ferruginous hardgroun
biserial foraminifer (probably Of the genus Deekerella)
Archaeocyath
(sponges)
chambered calcareous sponge forming part of the framework of this world-renowned reef complex.
Carbonates Mud
Definitions:
• Micrite - An abbreviation of “microcrystalline calcite”. The term is used both as a synonym for carbonate mud (or “ooze”) and for a rock composed of carbonate mud (calcilutite). Micrite consists of 1 to 4 µm-diameter crystals and forms as an inorganic precipitate or through breakdown of coarser carbonate grains. Micrite is produced within the basin of deposition and shows little or no evidence of significant transport (Folk, 1959).
• Microspar - Generally 5- to 20-µm-sized calcite produced by recrystallization (neomorphism) of micrite; can be as coarse as 30 µm (Folk, 1965). Restricted to recrystallization products, not primary precipitates.
• Pseudospar - A neomorphic (recrystallization) calcite fabric with average crystal size larger than 30-50 µm (Folk, 1965).
Keys to Petrographic Recognition:
1) Modern carbonate mud consists largely of the breakdown products of organisms (due to decomposition of organic binding materials and abrasion or maceration of shells). Macroscopic algae (especially green algae) are major contributors of needle-shaped, mud-sized, aragonitic particles in tropical platform and platform margin settings. Modern inorganic aragonitic precipitates, in the water column or on the seafloor, also are needle-like (with individual crystals typically 3-5 µm in length) and may contribute to carbonate muds.
2) The calcitic micrite of older carbonate rocks was neomorphically formed from mixed mineralogy precursors to form an equant mosaic of 1- to 4-µm crystals. The precursor material acted as detrital particles and so may show geopetal fabrics, scattered coarser particles, and other indications of mechanical sedimentation. Inclusions or molds of precursor minerals may be seen within micritic calcites (especially using SEM).
3) Neoformed microcrystalline cement and microbial precipitates may show clotted or peloidal fabrics and can grow in any position within interparticle pores or larger cavities (non-geopetal fabrics).
4) Microspar and pseudospar typically have patchy distributions grading into normal micrite; crystal outlines tend to be elongate (loaf-shaped) or have irregular, sutured boundaries).
Scholle, 2003
Carbonate mud (micrite) fills the lower part of the cavity while sparry calcite fills the upper part — the contact indicates an approximately level surface at the time of deposition
Here replacive calcite spar has embayed the originally smooth margins of a reworked (and thus substantially lithified) micritic intraclast
precipitated spar (the clear, coarse spar) and microspar formed by neomorphism of micritic matrix
sparsely fossiliferous micrite consists of a mix of nannoconids and other micritic material, including other finely comminuted skeletal particle
Micrite & Sparite
Micrite
Carbonate mud is termed micrite (0.03-0.04 mm)
Micrite can also form as a cryptocrystalline cement in certain circumstances.
Because of this it must be used with care as an index of depositional energy.
In conclusion, it would appear that lime mud, micrite, can form by a variety of processes.
Cement.
By definition this applies to crystal- line material that grows within the sediment fabric during diagenesis.
The most common cement in limestones is calcite, termed "spar" or sparite
Other cements in carbonate rocks include dolomite, anhydrite, and silica.
(x40) (D) Skeletal fragment with advanced calcite cementation. Sparry crystals have grown, with increasing size, both into the intergranular pores, and into the biomoldic pore caused by the solution of the orginal aragonite shell. (x60)
(A) Lime mudstone. Chalk, Upper Cretaceous, Beer, Devon. (x60)
(Selley, 2000)
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