Modul 7 - Igneous Rocks

7/28/2019 Modul 7 - Igneous Rocks

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Igneous RocksIgneous Rocks


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IGNEOUS ROCKSIGNEOUS ROCKS

Igneous Rocks form by crystallization of moltenIgneous Rocks form by crystallization of molten

rock materialrock material

Molten rock material below EarthMolten rock material below Earths surface iss surface is

calledcalled magmamagma

Molten rock material erupted above EarthMolten rock material erupted above Earthss

surface is calledsurface is called lavalava

The name changes because the compositionThe name changes because the compositionof the molten material changes as it is eruptedof the molten material changes as it is erupted

due to escape of volatile gasesdue to escape of volatile gases


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Rock Forming MineralsRock Forming Minerals

Temperat

uredecreases

SiO2ofliquidincreases

Olivine

Pyroxene

Amphibole

Biotite

Ca-rich

Na-rich

Ca-Na-rich

Na-Ca-rich

Quartz

Mus

covite

K-f

eldspar P

lag

ioc

lase

fel

dspar

D

iscontinuousbranch

Continuousbranch

BOWENS REACTION SERIES

1200C

700C

High

Low

Intermediate


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Olivine

Pyroxene

Amphibole

Biotite

Ca-rich

Na-rich

Ca-Na-rich

Na-Ca-rich

Quartz

Musco

vite

K-feldspar P

lag

io

cla

se

fe

lds

par

Dis

continuous

branch

Continuousbranch


Rock Forming MineralsRock Forming Minerals


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Rock Forming MineralsRock Forming MineralsHigh Temperature Mineral SuiteHigh Temperature Mineral Suite

OlivineOlivine

IsolatedIsolated TetrahedraTetrahedra StructureStructure

Iron, magnesium, silicon, oxygenIron, magnesium, silicon, oxygen

BowenBowens Discontinuous Seriess Discontinuous Series

AugiteAugite

Single Chain Structure (Pyroxene)Single Chain Structure (Pyroxene)

Iron, magnesium, calcium, silicon,Iron, magnesium, calcium, silicon,

aluminiumaluminium, oxygen, oxygen

BowenBowenss DiscontinuosDiscontinuos SeriesSeries

Calcium FeldsparCalcium Feldspar

Framework Silicate Structure (Plagioclase)Framework Silicate Structure (Plagioclase)

Calcium, sil icon,Calcium, sil icon, aluminiumaluminium, oxygen, oxygen

BowenBowens Continuous Seriess Continuous Series


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Rock Forming MineralsRock Forming MineralsIntermediate Temperature Mineral SuiteIntermediate Temperature Mineral Suite

HornblendeHornblende Double Chain Structure (Amphibole)Double Chain Structure (Amphibole)

Iron, magnesium, calcium, silicon,Iron, magnesium, calcium, silicon,

aluminiumaluminium, oxygen, oxygen BowenBowenss DiscontinuosDiscontinuos SeriesSeries

BiotiteBiotite

Sheet Silicate Structure (Mica)Sheet Silicate Structure (Mica) Iron, magnesium, potassium, silicon,Iron, magnesium, potassium, silicon,

aluminiumaluminium, oxygen, oxygen

BowenBowenss DiscontinuosDiscontinuos SeriesSeriesSodium FeldsparSodium Feldspar

Framework Silicate Structure (Plagioclase)Framework Silicate Structure (Plagioclase)

Sodium, silicon,Sodium, silicon, aluminiumaluminium, oxygen, oxygen BowenBowens Continuous Seriess Continuous Series


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Rock Forming MineralsRock Forming MineralsLow Temperature Mineral SuiteLow Temperature Mineral Suite

MuscoviteMuscovite Sheet Silicate Structure (Mica)Sheet Silicate Structure (Mica)

Calcium, potassium, sil icon,Calcium, potassium, sil icon, aluminiumaluminium,,

oxygenoxygen BowenBowenss DiscontinuosDiscontinuos SeriesSeries

Potassium FeldsparPotassium Feldspar

Framework Silicate Structure (Orthoclase)Framework Silicate Structure (Orthoclase) Potassium, silicon,Potassium, silicon, aluminiumaluminium, oxygen, oxygen

BowenBowens Continuous Seriess Continuous Series

QuartzQuartz Framework Silicate StructureFramework Silicate Structure

Silicon, oxygenSilicon, oxygen

Last to crystallize from magmaLast to crystallize from magma


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Olivine

Pyroxene

Amphibole

Biotite

Ca-rich

Na-rich

Ca-Na-rich

Na-Ca-rich

Quartz

Muscovite

K-fel

dspar P

lagio

cla

se

fe

lds

par

Dis

continuous

branch

C

ontinuousbranch


Rock Forming MineralsRock Forming MineralsBowenBowens Reaction Seriess Reaction Series


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R k F i Mi l


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Eff t f C li R t C t l SiEff t f C li R t C t l Si


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Effect of Cooling Rate on Crystal SizeEffect of Cooling Rate on Crystal Size

Crystals are formed by ions arranged inCrystals are formed by ions arranged in

orderly patternsorderly patterns Crystal size is determined by the rate ofCrystal size is determined by the rate of

coolingcooling

Extremely fast coolingExtremely fast cooling

Fast coolingFast cooling

Slow coolingSlow cooling



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Extremely fast coolingExtremely fast cooling

Forms glass, not crystalsForms glass, not crystals Occurs above EarthOccurs above Earthss

surface under water orsurface under water or

iceice Yields obsidian, volcanicYields obsidian, volcanic

glassglass




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Fast coolingFast cooling

Forms very smallForms very small

invisible crystalsinvisible crystals Crystallized out lessCrystallized out less

slowlyslowly

Magma moved moreMagma moved morerapidlyrapidly

Occurs closer to EarthOccurs closer to Earth ss

surfacesurface

Typical in smallTypical in small

intrusions and conduitintrusions and conduit


Eff t f C li R t C t l SiEffect of Cooling Rate on Cr stal Si e


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Slow coolingSlow cooling

Forms large, visibleForms large, visiblecrystalscrystals

The slower the coolingThe slower the cooling

rate, the larger therate, the larger the

crystals formedcrystals formed

Occurs below EarthOccurs below Earthss

surfacesurface

Typical of plutonic rocksTypical of plutonic rocks

Where do the igneo s rocks form?Where do the igneous rocks form?


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Volcanic (Extrusive)Volcanic (Extrusive)


Plutonic (intrusive)Plutonic (intrusive)


Where do the igneous rocks form?Where do the igneous rocks form?



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Where do the igneous rocks form?Where do the igneous rocks form?Plutonic (intrusive) Igneous RocksPlutonic (intrusive) Igneous Rocks

Plutonic (intrusive) Igneous RocksPlutonic (intrusive) Igneous Rocks

Form by crystallization of moltenForm by crystallization of molten

rock material below Earthrock material below Earths surfaces surface

CoarseCoarse--grained plutonic rocksgrained plutonic rocks

Crystallized out very slowly inCrystallized out very slowly in

large magma chambers 12large magma chambers 12--2020km beneath Earthkm beneath Earths surfaces surface

FineFine--grained plutonic rocksgrained plutonic rocks

Crystallized out less slowly,Crystallized out less slowly,

more rapidly, in smallmore rapidly, in smallintrusions and conduits closerintrusions and conduits closer

to Earthto Earths surfaces surface



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LaccolithsLaccoliths

are masses of igneous rock between layers ofare masses of igneous rock between layers of

the surrounding rockthe surrounding rock



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Dikes and SillsDikes and Sills

are tabular intrusive bodies.are tabular intrusive bodies.

Dikes cut across layer of the surrounding rockDikes cut across layer of the surrounding rock

Sills are injected between layers of strataSills are injected between layers of strata



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Where do the igneous rocks form?Where do the igneous rocks form?Volcanic (extrusive) Igneous RocksVolcanic (extrusive) Igneous Rocks

Volcanic (Extrusive) Igneous RocksVolcanic (Extrusive) Igneous Rocks

Form by crystallization of moltenForm by crystallization of molten

rock material above Earthrock material above Earths surfaces surface

LavasLavas

are flowing out (extruded)are flowing out (extruded)

PyroclasticPyroclastic volcanic rocksvolcanic rocks

are blasted outare blasted out

AshAsh

is very fineis very fine--

grainedgrained

pyroclasticpyroclastic

materialmaterial

BombsBombs

are largeare large

moltenmolten

blocks thatblocks that

are blastedare blasted

outout

BlocksBlocks

are largeare large

solidsolid blocksblocks

that arethat are

blasted outblasted out



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A lava fountainA lava fountain and rapidlyand rapidlyflowing basaltflowing basalt

Volcanic (extrusive) Igneous RocksVolcanic (extrusive) Igneous Rocks

PahoehoePahoehoe,, a smootha smooth--surfaced,surfaced,

ropy form of basalt thatropy form of basalt that

crystallizes out near thecrystallizes out near the

beginning of a basalt flowbeginning of a basalt f lowAA,AA, a jaggeda jagged--surfaced form ofsurfaced form ofbasalt that crystallizes out atbasalt that crystallizes out at

the end of a basalt flowthe end of a basalt flow Basalt, a mafic composition lavaBasalt, a mafic composition lava



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Andesite flow,Andesite flow,

Cascade Range, Oregon

Andesite flow,Andesite flow,

Mexico Cascade Range, OregonMexico

Andesite, an intermediate composition lavaAndesite, an intermediate composition lava



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Rhyolite dome,Rhyolite dome,

Mono Craters, CaliforniaMono Craters, California

Rhyolite flowRhyolite flow showing columnarshowing columnar

jointing,jointing, MacDougallsMacDougalls Island, NewIsland, New

BrunswickBrunswick

Rhyolite, a felsic composition lavaRhyolite, a felsic composition lava



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Pyroclastic Eruption,Pyroclastic Eruption, Eruption of Mount St. Helens,Eruption of Mount St. Helens,

Washington, 1980Washington, 1980




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Other NotableOther Notable PryoclasticPryoclastic Volcanic EruptionsVolcanic Eruptions

Igneous Rocks TextureIgneous Rocks Texture


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AA phaneriticphaneritic texturetexture

Consists of visible grainsConsists of visible grains

Is formed by veryIs formed by very slowslow

cooling below Earthcooling below Earth ss

surfacesurfaceCharacteristic ofCharacteristic ofplutonicplutonic

igneous rocksigneous rocks i.e.i.e. gabbrogabbro,,

diabasediabase, diorite, granite, diorite, granite



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Igneous Rocks Textureg

AphaniticAphanitic texturetexture

Consists of invisibleConsists of invisible

grains formed by fagrains formed by fast ratest rate

of coolingof cooling

Characteristic of theCharacteristic of thelavas:lavas: basalt,basalt, andesiteandesite,,

rhyoliterhyolite



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gg

Glassy textureGlassy texture

Consists of visible grainsConsists of visible grains

Is not crystalline, isIs not crystalline, is

formed by extremelyformed by extremely rapidrapid

coolingcoolingCharacteristic ofCharacteristic ofObsidianObsidian



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Vesicular textureVesicular texture

Is bubbly, formed byIs bubbly, formed by

trapped bubbles of gastrapped bubbles of gas

Characteristic ofCharacteristic ofscoriascoria

(vesicular basalt) and(vesicular basalt) andpumicepumice (vesicular(vesicular

rhyoliterhyolite))

gg



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gg

PorphyriticPorphyritic texturetextureConsists ofConsists ofphaneriticphaneritic

(visible) grains in an(visible) grains in an

aphaniticaphanitic matrixmatrixPhaneriticPhaneritic crystals form bycrystals form by

very slow cooling belowvery slow cooling below

EarthEarths surfaces surface

AphaniticAphanitic crystals form bycrystals form byvery rapid cooling abovevery rapid cooling above

EarthEarths surfaces surface

Characteristic of theCharacteristic of the

lavas:lavas: basaltbasalt ,, andesiteandesite,,rhyoliterhyolite

Formed when a lava isFormed when a lava is

erupted as a crystal musherupted as a crystal mush

Texture and where they formTexture and where they form


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yy

Based on Where They FormBased on Where They Formand Their Textureand Their Texture

PhaneriticPhaneritic TextureTexture

AphaniticAphanitic TextureTexture

Glassy TextureGlassy Texture Vesicular TextureVesicular Texture

PorphyriticPorphyritic TextureTexture

Volcanic (Extrusive) Igneous RocksVolcanic (Extrusive) Igneous RocksPlutonic (intrusive) Igneous RocksPlutonic (intrusive) Igneous Rocks

BELOW EARTHBELOW EARTHS SURFACES SURFACE

ABOVE EARTHABOVE EARTHS SURFACES SURFACE

CLOSER EARTHCLOSER EARTHS SURFACES SURFACE

Igneous Rocks CompositionIgneous Rocks Composition


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g

UltramaficUltramafic

Means rich inMeans rich in magnesiummagnesium

andand ironiron Is the average compositionIs the average composition

of Earthof Earths mantles mantle

Composed of olivine andComposed of olivine andaugiteaugite

Example:Example: peridotiteperidotite

DunitDunit (Olivine rich)(Olivine rich)

HarzburgitHarzburgit (Pyroxene rich)(Pyroxene rich)



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MaficMafic

Means rich inMeans rich in magnesium,magnesium,

iron, and/or calciumiron, and/or calcium Is the average compositionIs the average composition

of oceanic crustof oceanic crust

Composed of olivine,Composed of olivine,augiteaugite, and calcium,, and calcium,

plagioclase feldsparplagioclase feldspar

Examples:Examples: basalt,basalt, diabasediabase,,

andand gabbrogabbro



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IntermediateIntermediate

MeansMeans halfhalfmaficmafic, half, half

felsicfelsic Is the composition of aIs the composition of a

mixture of oceanic andmixture of oceanic and

continental crust?continental crust? Composed of hornblendeComposed of hornblende

and calciumand calcium--sodiumsodium

plagioclase feldsparplagioclase feldspar

Examples:Examples: andesiteandesite andand

dioritediorite



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FelsicFelsic

Means rich inMeans rich in feldsparfeldsparandand

silicasilica Is the average compositionIs the average composition

of continental crustof continental crust

Composed of potassiumComposed of potassiumfeldspar, sodiumfeldspar, sodium

plagioclase feldspar,plagioclase feldspar,

quartzquartz

Examples:Examples: rhyoliterhyolite andand

granitegranite

Classification and naming of igneous rocksClassification and naming of igneous rocks


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Identification of Plutonic Igneous RocksIdentification of Plutonic Igneous Rocks

Plutonic Rocks

Phaneritic texture

Mafic compositionDark gray

Diabase(fine-grained)

Gabbro(coarse-grained)

Intermediate compositionMedium gray,

~ 50:50 black and white

Diorite

Felsic compositionLight gray

or pink

Granite

Identification of Volcanic Igneous RocksIdentification of Volcanic Igneous Rocks



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g

Volcanic Rocks

Glassy texture

Obsidian

Vesicular texture

ScoriaMafic compositionDark gray

PumiceFelsic composition

Light gray

Aphaniticmatrix

The lavas

BasaltMafic composition

Dark gray

AndesiteIntermediate composit ion

Medium gray orgreenish gray

Usually porphyritic

RhyoliteFelsic composition

Light grayor pink

Identification of Plutonic Igneous RocksIdentification of Plutonic Igneous Rocks

TEXTUREORIGIN AND EVOLUTION OF IGNEOUS ROCKSORIGIN AND EVOLUTION OF IGNEOUS ROCKS


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Temperatu

redecreas

es

SiO2

ofliquidincreases

Olivine

Pyroxene

Amphibole

Biotite

Ca-rich

Na-rich

Ca-Na-rich

Na-Ca-rich

Quartz

Musc

ovite

K-fe

ldspar P

lag

ioc

lase

fe

ldspar

Discontinuou

sbranch

C

ontinuous

branch

Volcanic

G

ABBRO

D

IORITE

ANDESITEB

ASALT

GRANIT

E

RHYOLITE

AphaniticPhaneritic

Plutonic

ORIGINBOWENS REACTION SERIES

PERIDOTITE



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Obsidian (volcanic glass)Obsidian (volcanic glass)


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Scoria (vesicular basalt)Scoria (vesicular basalt)


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Pumice (vesicular rhyolite)Pumice (vesicular rhyolite)


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BasaltBasalt


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Porphyritic AndesitePorphyritic Andesite


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RhyoliteRhyolite


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GabbroGabbro


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DioriteDiorite


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GraniteGranite


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Modul 7 - Igneous Rocks