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Ferro-Magnesium

(Mafic) Minerals

Non-Ferro-Magnesium

(Feldspar) Minerals

Olivine

Pyroxene

Amphibole

Bioti te

CaPlagioclase

NaPlagioclase

Ca/Na

Orthoclase

Muscovite

Quartz

isolatedSi04

singlechain

doublechain

Sheet

BOWEN'S REACTIONSERIES

ANDTHEIGNEOUS ROCKFORMINGMINERALS

light green, glassy,often as small grains

dark green/black; dullblocky; 90o cleavage

black, shiny, elongate,crystals; 60-120o cleavage

black, very shiny, inthin very smooth sheets

pink, white, greenish; twocleavages 90o; opaque

glassy, clear, often appearsgray in rocks; no cleavage

white to brassy thin sheets;clear; very smooth

white; 90o cleavage;striations sometimes;appears translucent

white; 90o cleavage;striations sometimes;appears translucent

dark, almost black to lightgray; 90o cleavage; striationsand/or irridesence

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3. What are the most common minerals in igneous rocks? Why is it so abundant?

Feldspar groups comprisesseveral individual chemical

species in aluminosilicatesframework which are themost abundant elements inthe earth.

Feldspars exhibit varioussolid solution that allow toform in various chemical

compositional conditions.

Anorthite

Orthoclase

Albite plagioclas

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4. What minerals can be used to estimate if this rock is formed from (1) silica-oversaturated(2) silica-saturated and (3) silica-undersaturated magmas?

Silica-oversaturated: silica minerals such as quartz, cristobalite,tridymite, coesite.

Silica-saturated: rocks contain neither silica nor silica-deficientminerals like nepheline [(Na, K)AlSiO4] or olivine [(Mg, Fe)SiO4].

Silica-undersaturated:

Nepheline-NaAlSiO4,Leucite - KAlSi2O6

ForsteriticOlivine -Mg2SiO4

Sodalite - 3NaAlSiO4 .NaCl

Nosean - 6NaAlSiO4 .Na2SiO4

Hayne - 6NaAlSiO4.)Na2,Ca(SiO4

Perovskite - CaTiO3Melanite - Ca2Fe+3Si3O12

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1. According to IUGS classification, please identify the corresponding rocks according to their

mineral composition:

(a) For a pluton rock: 20%

alkali-feldspar + 40% quartz

+ 20% plagioclase + 20%

mafic minerals

NORMALIZED BY

MAFIC MINERALS:

-alkali-feldspar: 25%

-quartz: 50%

-plagioclase: 25%

GRANITE

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(b) For a volcanic rock: 30% alkali-feldspar + 30% plagioclase + 30% feldspathoid +

10% mafic minerals

NORMALIZED BY

MAFIC MINERALS:-alkali-feldspar: 33%

-plagioclase: 33%

-feldspathoid: 33%

tephritic phonolite or phonolitic

tephrite are possible

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(c) For a mafic pluton rock: 30% Hornblende + 20% plagioclase + 30% pyroxene +20%olivine:

Hornblende > Olivine

normalized by olivine

-Hornblende: 37.5 %-plagioclase: 25%

-pyroxene: 37.5%

pyroxene-hornblende gabbro

or

pyroxene-hornblende noritegabbro: clinopyroxene

norite: orthopyroxene

gabbronorite: both

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Euhedral (): Crystals in an igneous rocks have ideal shapes and

completely bounded by well developed crystal faces. Mostly occurs when the

magma is still largely liquid. It is commonly the earliest phenocryst mineral.

Subhedral(): When crystals grow in forms similar to their ideal formsbut are only partly bounded by crystal faces.

Anhedral ():Highly irregular grains that give no indication of idealcrystal form.

zircon apatitepyrite

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Poikilitic (): A late

crystallized mineral completely

encloses numerous small grains

of other minerals. The most

common enclosed mineral is

mica which is typically the

latest crystallized minerals

from most magmas.http://z.about.com/d/geology/1/0/n/J/1/poikilitictexture.jpg

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Trachytic (): Commonly found in

volcanic rocks. The texture has a strong

parallel alignment of plagioclase laths that

reflects compaction or flow of the magma

during crystallization.

http://www-odp.tamu.edu/publications/180_SR/176/plates/2_5.jpg

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Graphic texture: relatively common in granites and

pegmatite and involves an intergrown of quartz and alkali

fe ldspar in which thin bleb of quartz lie in

crystallographically controlled orientation with large alkali

feldspar. It occurs when two minerals crystallize

simultaneously. http://upload.wikimedia.org/wikipedia/commons/f/fd/Graphic-texture.jpg

Exsolution texture (): chemical

decompos i t i on of an orig inal ly

homogeneous solid solution mineral into

two more nearly end member minerals

during cooling. ex. perthite ()http://www.answers.com/topic/perthite

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Ophitic (): in fine to medium-grained mafic rocks and refers to the enclosure of

plagioclase laths by larger, subhedral augite grains. When augite grains are not large enough

to enclose plagioclase lath, the texture is called subophitic. (Crystallization simultaneously)

Trachytic (): Commonly found in volcanic rocks. The texture has a strong parallel

alignment of plagioclase laths that reflects compaction or flow of the magma during

crystallization.

Graphic texture: relatively common in granites and pegmatite and involves an intergrown of

quartz and alkali feldspar in which thin bleb of quartz lie in crystallographically controlled

orientation with large alkali feldspar. It occurs when two minerals crystallize simultaneously.

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Trachytic (): Commonly found in volcanic rocks. The texture has a strong

parallel alignment of plagioclase laths that reflects compaction or flow of the magma

during crystallization.

Graphic texture: relatively common in granites and pegmatite and involves an intergrown of

quartz and alkali feldspar in which thin bleb of quartz lie in crystallographically controlled

orientation with large alkali feldspar. It occurs when two minerals crystallize

simultaneously.

Exsolution texture (): chemical decomposition of an

originally homogeneous solid solution mineral into two more

nearly end member minerals during cooling. ex. perthite (

)

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1.

(a)(b)(c)

Ferro-Magnesium

(Mafic) Minerals

Non-Ferro-Magnesium

(Feldspar) Minerals

Olivine

Pyroxene

Amphibole

Biotit e

CaPlagioclase

NaPlagioclase

Ca/Na

Orthoclase

Muscovite

Quartz

isolatedSi04

singlechain

doublechain

Sheet

BOWEN'S REACTION SERIES

AND THEIGNEOUS ROCKFORMING MINERALS

lightgreen, glassy,oftenas small grains

darkgreen/black;dullblocky;90o cleavage

black,shiny, elongate,crystals;60-120o cleavage

black,very shiny,inthinvery smooth sheets

pink,white, greenish;twocleavages90o;opaque

glassy,clear,often appearsgrayinrocks;nocleavage

whiteto brassythin sheets;clear;very smooth

white; 90o cleavage;striations sometimes;appears translucent

white; 90o cleavage;striations sometimes;appears translucent

dark, almost black to lightgray; 90o cleavage; striationsand/or irridesence

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3. (a)Granite(b)Diorite(c)

(d) (Basalt) P.

88-95

(a)::

(b)::

(c)::OscillatoryZoning

(d):

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4.

P.120-125

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:

1. Anorthite (Ca-feldspar)Albite (Na-Feldspar)60% An + 40% Ab:

(a)

1480C1380C

(b)1400C

Plagioclase70%30%

An32-Ab68

2. Albite (Na-Feldspar)Orthoclase (K-Feldpsar)(a)Eutectic point)600C

(b)30% Ab+ 70% Or700C

700COr-rich feldspar

40%+60%Ab30-Or70

(c)600CperthiteOr-richAb-rich feldspar

(d)50% Ab+ 50% Or500C

Or77-Ab23Or7-Ab93

42%58%

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3. ForsteriteSilica:(a)20% Fo+ 80% Si1700C

Fo20-Si80

(b)70% Fo+ 30% Si1557C1500C

ForsteriteEnstatite1500CForsterite

Enstatite

(c)55% Fo+ 45% Six1500C

1500CEnstatite75%

25%Si70-Fo30

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:1.

-

- pH

CO2

2. (pp.211-215)3. (pp.152-153)

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:1. Whats the different between roundness and sphericity?

-Roundness()

- Sphericity:()/()[()/)]

1/3

Ex.Va4/3(a/2)3 =a3/6 a3/6

[(d3/6)/ a3/6]1/3 (d/a)

2. Please describe the maturing of a sedimentary rock from viewpoint of (a) mineralcomposition (b) grain shape (c) grain size

(a) ionic potentialK

+,Na

+, Ca2+

ionicpotentialAl

3+,Si

4+

(b)-(c)

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3. Suppose you wanted to determine the relative amounts of sandstone, mudrock andcarbonate rock in earth crust, what sedimentary factor would you have to consider?

(a)Sandstones: composed of fragmental sediment around 2.0 mm to 0.06mm in diameter. It indicates an sedimental environment of relatively

high kinetic energies shallow marine, river channel or desert (rare).

(b) Mudrocks: composed of fragmental sediment < 62 m in diameter. Itindicates a quite-water environment of relatively deep sea or quite

lakes.

(c)Carbonate rock: originates from hard parts of marine organism. It issignificant of very shallow marine within 10m below sea level.

4. Explain why grain size is an important factor in the textural analysis of sandstones.What information can it provides about the origin of the rocks? Please describe in

terms of settling velocity and movement of grains. (pp.141-

pp.147)

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