SlideShare a Scribd company logo
1 of 45
GE 106 
Lecture 2
Igneous Rocks 
By 
Moustafa Hashad 
Three Lectures 
Lecture - 1 
Attendance ??
Table of Contents 
Lecture 1 Lecture 2 
What are Rocks? 
 Major Rock Types 
 The Rock Cycle 
 Nature, and Origin of 
Igneous Rocks 
 Igneous Rocks 
 What happens to 
molten rock as it 
cools? 
 Crystal size and 
Cooling Rates 
 Texture, Igneous Rock 
Textures 
 Phaneritic , 
Aphanitic , 
Porphyritic Glassy 
, Pegmatitc 
 Pyroclastic Aa Lava, 
Pahoehoe 
Lecture 3 
Structures of 
Igneous Rocks. 
Mineral 
Composition 
Magma and 
Bowen Reaction 
Series 
Mineral 
Composition and 
Magma 
Ferromagnesian 
Silicates 
Non- 
Ferromagnesian 
Silicates 
Classification of Igneous 
Rocks. 
*Color/Texture Igneous 
Classification 
**Modal Igneous 
Classification 
*** Normative Igneous 
Classification 
Igneous Rock Categories 
Granitic, Basaltic, 
Andesitic Igneous Rocks 
Several types of Igneous 
Rocks: 
Granite, Rhyolite, Pumice, 
Obsidian, Gabbro, Basalt, 
Andesite, Diorite, Tuff.
Part 1 
and 
Major Rock Types
What are Rocks? 
Most rocks are an aggregate of one or more 
minerals and a few rocks are composed of 
non-mineral matter. 
There are three major rock types: 
 1. Igneous 
 2. Metamorphic 
 3. Sedimentary 
5 
Table of Contents
Major Rock Types 
 Igneous rocks are formed by the cooling of molten 
magma or lava near, at, or below the Earth’s surface. 
 Sedimentary rocks are formed by the lithification 
of inorganic and organic sediments deposited near or at 
the Earth’s surface. 
 Metamorphic rocks are formed when preexisting 
rocks are transformed into new rocks by heat and 
pressure, usually below the Earth’s surface. 
6 
Table of Contents
Major Rock Types 
Although the three rock 
Categories are connected 
in the Endless rock cycle, 
igneous rocks 
Are traditionally taught 
first. Remember details of rock cycle
9 
Table of Contents
Nature, and Origin 
of 
Igneous Rocks
Igneous Rocks 
How to Tell Igneous Rocks 
 The main thing about Igneous rocks is that they were 
once hot enough to melt. The following features are all 
related to that. 
 Because their mineral grains grew together tightly as 
the melt cooled, they are relatively strong rocks. 
 They're made of primary minerals that are mostly black, 
white or gray. Any other colors they may have are pale.
Igneous Rocks 
Origin of Igneous Rocks 
The word "igneous" comes from the Latin for fire, and 
1- Igneous rocks, in common, have formed by the cooling 
and crystallization of a melt. 2- This material may have been: 
a- lava erupted at the Earth's surface, and or 
b- Magma (un-erupted lava) at depths of up to a few kilometers 
(shallow magma), or c- Magma in deeper bodies (plutons). 
Those three different settings create three main types of igneous 
rocks: 
1- Rock formed of lava is called Extrusive Rocks 
2- Rock from shallow magma is called Hypabyssal 
intrusive Rocks and 
3- Rock from deep magma is called Plutonic intrusive 
Rocks 
The deeper the magma, the slower it cools and the larger the
Origin of Igneous Rocks 
هذه الشريحة و التالية 
تكرار للشريحة السابقة 
 Igneous rocks are formed by the cooling of 
molten rock. 
 There are two major states of molten rock: Magma and 
Lava. 
 Magma is a form of molten rock that exists below the 
Earth’s surface. 
 Lava is the term given to magma once it reaches the 
Earth’s surface, usually in the form of a volcanic eruption. 
 There are two major classifications of igneous rocks: 
Intrusive and Extrusive. 
 Intrusive igneous rocks are formed by magma that 
cools below the Earth’s surface: a - at shallow depth 
(Old name Hypabyssal Rocks). And, b - at deep depth 
.(Old name Plutonic Rocks) 
 Extrusive igneous rocks are formed by lava that cools 
at the Earth’s surface. (Old name Volcanic Rocks) 
13 
Table of Contents
Igneous Rocks 
 Intrusive igneous rocks generally cool very slowly 
below the earth’s surface or as the magma is rising 
to the earth’s surface. 
Hypabyssal 
Hypabyssal igneous rocks are formed at a depth in between the 
plutonic and volcanic rocks. These are formed due to cooling 
and resultant solidification of rising magma just beneath the 
 
earth surface. Hypabyssal rocks are less common than plutonic 
or volcanic rocks and often form dikes, sills, laccoliths, lopoliths, 
or phacoliths 
 Extrusive igneous rocks generally cool quickly when they 
reach the earth’s surface usually through volcanoes or 
fissure. 
14 
Table of Contents
Igneous Rocks 
Igneous rocks form in three main places: 
1- where the tectonic plates 
pull apart (at mid-ocean ridges), 
2- where plates 
come together 
(at subduction zones) 
and 
3- where continents 
are pushed together, 
making the Earth's crust thicker 
and allowing it to heat to melting.
What happens 
to 
molten rock 
as 
it cools?
What happens to molten rock as it cools? 
1 - When the temperature of molten rock begins 
to drop there is a loss of energy that causes 
ions to slow down. As the ions slow down, they 
group together and arrange themselves into 
definit crystalline structures. This process is 
referred to as crystallization. 
 So, What is the definition of crystallization ?? 
 Definition: 
 Crystallization: 
It is the process where the temperature of molten 
rock begins to drop, so, there is a loss of 
energy that causes ions to slow down. As the 
ions slow down, they group together and 
arrange themselves into a crystalline structures. 
17 
Table of Contents
What happens to molten rock as it cools? Cont. 
2 - During crystallization, the silicon and oxygen atoms 
are the first to link together forming silicon-oxygen 
tetrahedrons, which are the building block of all silicate 
minerals. 
3 - As crystallization continues, 
these individual silicon-oxygen 
tetrahedrons join with one 
another, and other ions, to 
form the basic structure of 
most minerals and igneous rocks.
What happens to molten rock as it cools? Cont. 
4 - Environmental conditions including temperature 
and the presence of water or gases during 
crystallization affect the composition, the size, 
and the arrangement of the mineral grains. 
The size and arrangement of mineral crystals, 
(usually referred to crystals as grains), define the 
texture of the rock. 
So, 
 Geologists use mineral and textural 
classifications to infer information about the 
environmental setting in which different igneous 
rocks are formed. 
19 
Table of Contents
Crystal size 
and 
Cooling Rates
Crystal Size and Cooling Rates 
 Slower cooling rates produce 
larger individual crystals in 
the rock 
 Intrusive igneous rocks 
generally cool very slowly 
and tend to have large 
crystals that produce a 
course-grained rock. 
Phaneritic rocks are 
coarse-grained rocks 
which contain individual 
crystals that are relatively 
even in size and large 
enough for scientists to 
identify the different 
mineral grains that 
compose the rock. 
21 
Table of Contents
Crystal Size and Cooling Rates 
 Faster cooling rates produce 
smaller individual crystals in 
the rock 
 Extrusive igneous rocks 
tend to cool quickly and 
are characterized by 
smaller grains that 
produce a fine-grained 
rock. 
Aphanitic is the term 
used to describe very fine 
grained rocks. 
22 
Table of Contents
Crystal Size and Cooling Rates- C0nt. 
 Porphyritic textured rocks contain both a 
coarse and fine-grained texture. 
 The coarse grains in a porphyritic rock 
begin to develop as the magma is cooling 
below the surface of the earth. Following 
eruption or exposure to lower 
temperatures, the remaining magma or lava 
cools very quickly and forms minerals with 
fine-grained textures. 
 As a result, porphyritic textures contain 
both coarse- and fine–grained minerals. 
23 
Table of Contents
Texture 
and 
Igneous Rock Textures
Texture 
Definition: 
Texture 
Texture is a term used to describe the size, shape, and 
arrangement of interlocking crystallized mineral 
grains in an igneous rock. 
 Two major factors affect the size of crystal grains in 
an igneous rock: 
 1) Rate of cooling at which molten rock cools; 
Slow …… or ….. fast 
 2) Amount of dissolved gases or fluids in the 
magma. 
25 
Table of Contents
Texture Cont. 
 Igneous minerals vary greatly in grain size. Grain-size classes 
are similar to the sedimentary scale, but there are fewer 
divisions with a greater range of size. 
 Phenocrysts are grains in an igneous rock that are larger 
than the other grains that make up the rest of the rock. 
26 
Grain Size 
Categories 
Grain Size Divisions 
fine grained = < 1 mm 
medium grained = 1 mm < 5 mm 
coarse grained = 5 mm < 3 cm 
very coarse-grained = > 3 cm 
Phenocrysts Texture 
microphenocrysts = 0.03 mm – 0.3 mm 
phenocrysts = 0.3 mm – 5 mm 
megaphenocrysts = > 5 mm 
Table of Contents
Igneous Rock Textures - 1 
 Phaneritic (Intrusive) 
 Aphanitic (Extrusive) 
 Porphyritic (Intrusive and Extrusive) 
 Glassy (Extrusive) 
Pegmatitic (Intrusive) 
 Pyroclastic Materials (Extrusive) 
 Aa Lava (Extrusive) 
 Pahoehoe Lava (Extrusive) 
27 
Table of Contents
Phaneritic Texture 
Phaneritic (Intrusive) 
Phaneritic rocks are coarse-grained rocks which form below the Earth’s 
surface. 
The individual crystals are relatively even-sized and large enough for 
scientists to identify the different mineral grains that compose the rock. 
28 
Quartz Crystals: 
(White) 
Feldspar Crystals: 
(Pink) 
Biotite Crystals: 
(Black) 
Granite rock with a phaneritic texture 
Table of Contents 
Igneous Rock Textures - 2
Aphanitic Texture 
 Aphanitic (Extrusive) 
 Definition: Aphanitic rocks are very fine-grained 
and contain crystals that are too 
small to distinguish without the aid of a 
magnifying lens. 
 Aphanitic rocks are often described by how 
light or dark the rock appears. 
Lighter colored aphanitic rocks contain mostly 
non-ferromagnesian silicate minerals. 
Darker colored aphanitic rocks contain mostly 
ferromagnesian silicate minerals. 
Aphanitic rocks may also contain vesicles 
of remnant gas that give the rock a 
vesicular texture. 
Vesicles form when the rock cools very 
quickly and preserves the openings 
formed by the expansion of trapped gas 
bubbles. 
29 
Basalt rock with an 
aphanitic 
and vesicular texture 
Table of Contents 
Igneous Rock Textures - 3
Porphyritic Texture 
 Porphyritic (Intrusive and Extrusive) 
Definition: Porphyritic rocks 
contain both coarse- and fine-grained 
textures indicating different 
environmental conditions which 
formed the rock. 
The coarse grains in a porphyritic 
rock develop as the magma is 
cooling below the surface of the 
earth. 
The fine-grained component of a 
porphyriic rocks forms when the 
magma or lava cools faster. 
The large coarse-grained crystals are 
referred to as phenocrysts. 
The small fine-grained crystals are 
referred to as groundmass. 
30 
Rhyolite rock with 
porphyritic texture containing 
phenocrysts of olivine and 
pyroxene and a gabbro 
groundmass. 
Table of Contents 
Igneous Rock Textures - 4
Porphyritic 
Texture 
Definition: 
Large crystals 
called 
phenocrysts are 
surrounded by 
an aphanitic 
matrix or 
groundmass.
Images for porphyritic textures
Images for porphyritic textures
Glassy Texture 
 Glassy (Extrusive) 
 Definition: Glassy textured rocks are formed by very rapid cooling of 
magma. 
Obsidian rock with a glassy 
texture and conchoidal 
Glassy rocks often form from magmas with 
high silica content that arranges into long 
chainlike structures before crystallization occurs. 
These silica chains increase the viscosity of the 
magma and it once it eventually cools it forms a 
glassy textured rock. 
Glassy rocks can be considered amorphous 
because they have no crystalline structure. 
fractures 
 Glassy rocks are classified by the amount of glass contained by the rock: 
 Glass-bearing: 0-20% glass, Glass-rich: 20-50% glass 
 Glassy: 50 – 100% glass 
 Obsidian is a common glassy rock. 36 
Table of Contents 
Igneous Rock Textures - 5
Pegmatitic Texture 
 Pegmatitic (Intrusive) 
veins extending through rock 
 Definition: Pegmatitic rocks 
contain large interlocking 
crystalline grains > 1-2 centimeter in 
diameter. 
Examples of pegmatitic 
Pegmatites are commonly composed of quartz, 
feldspar, and mica minerals. 
Pegmatites form from a combination of hydrothermal 
and igneous processes; and is dependant on the 
presence of fluids and volatiles such as water, 
chlorine, bromine, sulfur, and fluorine. 37 
Table of Contents 
Igneous Rock Textures - 6
Pegmatitic Texture 
Pegmatites form late in the 
crystallization process when 
there are a lot of fluids 
present in the molten rock. 
The fluids enable individual 
ions to move around more 
freely, ultimately bonding to 
form very large crystals. 
 Pegmatitic dikes form 
around the margins of 
intrusive plutons, or 
occasionally as veins of 
rock which extend into the 
pluton. 
Examples of pegmatitic veins 
38 
extending through rock 
Table of Contents 
Igneous Rock Textures – 6a
Pyroclastic Materials 
 Pyroclastic (Extrusive) 
Pyroclastic materials form when individual rock 
fragments are ejected during a violent volcanic 
eruption and consolidate into larger rock composites 
when they deposit on the surface. 
Tuff rock with 
pyroclastic material. 
 Pyroclastic rocks contain at least 75% pyroclastic fragments with the 
remainder consisting of other inorganic sediments or organic 
materials. 
 Pyroclastic rocks contain a mixture of different types of particles that 
are not cohesively joined by interlocking crystals, but instead are 
consolidated masses of multiple rock fragments. 
Tephra is the term used to describe pyroclastic 
sediments. 
39 
Table of Contents 
Igneous Rock Textures - 7
Pyroclastic Fragments 
 Pyroclastic materials do not conform well to igneous grain size 
classifications. Instead, geologists use the following terms to 
describe pyroclastic fragments: 
 Bombs: fragments with a mean diameter > 64 mm, and a 
rounded shape. 
 Blocks: fragments with a mean diameter > 64 mm, and a 
blocky, angular shape. 
 Lapilli: fragments in any shape with a mean diameter of 2- 
64 mm. 
 Ash: grains of pyroclastic fragments with a mean diameter 
< 2 mm. This includes coarse ash grains (0.032 -2 mm) and 
fine ash grains (< 0.032 mm). 
40 
Table of Contents 
Igneous Rock Textures - 8
Aa 0r aa Lava 
 Aa Lava (Extrusive) 
 Aa is a basaltic lava flow that has a rough surface, 
characterized by sharp and jagged blocks. 
 Aa flows move slowly (5-50 meters per hour) and 
are often several meters thick. 
 As aa lava flows, the outer surface and advancing 
edge cools first 
 Aa lava flows are common on the Hawaiian 
Islands. The aa flows move so slowly that tourists 
can walk up to them and take pictures. 
Aa lava in Hawaii’s 
Volcanoes National Park. 
41 
Table of Contents 
Igneous Rock Textures - 9
Pahoehoe Lava 
 Pahoehoe Lava (Extrusive) 
Pahoehoe (pronounced pah-hoy-hoy) is a 
basaltic lava flow that has a smooth and 
twisty, rope-like surface. 
The characteristic ropy texture forms as 
the surface lava cools while the molten 
material beneath it is still moving. The 
tension formed by the cooling lava 
causes it to wrinkle as the subsurface 
lava continues to flow. As a result the 
surface cools in a series of overlapping, 
ropy lobes. 
Pahoehoe lava flows move slow enough 
(5-50 meters per hour) for observers to watch the 
cooling lava as it advances forward. 
42 
Pahoehoe lava 
flows in Hawaii. 
Table of Contents 
Igneous Rock Textures - 10
IGNEOUS INTRUSIONS / PLUTONS 
intrusions/ plutons 
As magma cools underground, it will begin to solidify within 
Earth's crust. Once completely crystallized, these masses of 
igneous intrusive rock are referred to as intrusions or as 
plutons (after Pluto, Greek god of the underworld). Both terms 
are used interchangeably by geologists, so take your pick. 
Dikes - are relatively small 
igneous intrusions formed as 
magma penetrates into rock 
fractures and solidifies into thin, 
sheet-like bodies. Where dikes 
are very abundant they are 
referred to as dike swarms. 
Three-inch thick dike 
formed within a larger mass 
of granite
44
End 
Of 
Lecture 2

More Related Content

What's hot

Process of Transport and Generation of Sedimentary Structures
Process of Transport and Generation of Sedimentary StructuresProcess of Transport and Generation of Sedimentary Structures
Process of Transport and Generation of Sedimentary StructuresAkshayRaut51
 
SEDIMENTARY STRUCTURES
SEDIMENTARY STRUCTURESSEDIMENTARY STRUCTURES
SEDIMENTARY STRUCTURESSaad Raja
 
Introduction to diagenesis
Introduction to diagenesisIntroduction to diagenesis
Introduction to diagenesisWajid09
 
Mantle melting and Magmatic processes
Mantle melting and Magmatic processesMantle melting and Magmatic processes
Mantle melting and Magmatic processesAnanya21Mittal
 
Ch 10 magma generation
Ch 10 magma generationCh 10 magma generation
Ch 10 magma generationRaghav Gadgil
 
Magmatic Differentiation.pptx
Magmatic Differentiation.pptxMagmatic Differentiation.pptx
Magmatic Differentiation.pptxBARKAVE BALUSAMY
 
Sedimentary Rock Classification
Sedimentary Rock ClassificationSedimentary Rock Classification
Sedimentary Rock ClassificationM.T.H Group
 
Geochemical methods in mineral exploration
Geochemical  methods  in  mineral  explorationGeochemical  methods  in  mineral  exploration
Geochemical methods in mineral explorationPramoda Raj
 
Paired metamorphic belts
Paired metamorphic beltsPaired metamorphic belts
Paired metamorphic beltsPramoda Raj
 
Classification of ore deposits
Classification of ore depositsClassification of ore deposits
Classification of ore depositsAbdul Bari Qanit
 
Classifications of igneous rocks
Classifications of igneous rocksClassifications of igneous rocks
Classifications of igneous rocksPramoda Raj
 

What's hot (20)

Process of Transport and Generation of Sedimentary Structures
Process of Transport and Generation of Sedimentary StructuresProcess of Transport and Generation of Sedimentary Structures
Process of Transport and Generation of Sedimentary Structures
 
SEDIMENTARY STRUCTURES
SEDIMENTARY STRUCTURESSEDIMENTARY STRUCTURES
SEDIMENTARY STRUCTURES
 
Metamorphic rocks
Metamorphic rocksMetamorphic rocks
Metamorphic rocks
 
Anorthosite
Anorthosite Anorthosite
Anorthosite
 
Introduction to diagenesis
Introduction to diagenesisIntroduction to diagenesis
Introduction to diagenesis
 
Mantle melting and Magmatic processes
Mantle melting and Magmatic processesMantle melting and Magmatic processes
Mantle melting and Magmatic processes
 
THE ORE-BEARING FLUIDS
THE ORE-BEARING FLUIDSTHE ORE-BEARING FLUIDS
THE ORE-BEARING FLUIDS
 
Ch 10 magma generation
Ch 10 magma generationCh 10 magma generation
Ch 10 magma generation
 
Magmatic Differentiation.pptx
Magmatic Differentiation.pptxMagmatic Differentiation.pptx
Magmatic Differentiation.pptx
 
Stratigraphic Code
Stratigraphic CodeStratigraphic Code
Stratigraphic Code
 
Fluid inclusion in ores
Fluid inclusion in oresFluid inclusion in ores
Fluid inclusion in ores
 
Sedimentary Rock Classification
Sedimentary Rock ClassificationSedimentary Rock Classification
Sedimentary Rock Classification
 
Carbonate rocks
Carbonate rocksCarbonate rocks
Carbonate rocks
 
Geochemical methods in mineral exploration
Geochemical  methods  in  mineral  explorationGeochemical  methods  in  mineral  exploration
Geochemical methods in mineral exploration
 
Carbonatites
CarbonatitesCarbonatites
Carbonatites
 
Lecture 10 textures of ore deposits and associated features
Lecture 10 textures of ore deposits and associated featuresLecture 10 textures of ore deposits and associated features
Lecture 10 textures of ore deposits and associated features
 
Paired metamorphic belts
Paired metamorphic beltsPaired metamorphic belts
Paired metamorphic belts
 
Classification of ore deposits
Classification of ore depositsClassification of ore deposits
Classification of ore deposits
 
Classifications of igneous rocks
Classifications of igneous rocksClassifications of igneous rocks
Classifications of igneous rocks
 
Wall Rock Alteration.pdf
Wall Rock Alteration.pdfWall Rock Alteration.pdf
Wall Rock Alteration.pdf
 

Similar to Igneous rock ge 106

Igneous rocks bs 1st year
Igneous rocks  bs 1st yearIgneous rocks  bs 1st year
Igneous rocks bs 1st yearAwais Bakshy
 
II.A Minerals and Rocks
II.A Minerals and RocksII.A Minerals and Rocks
II.A Minerals and RocksSimple ABbieC
 
Rocks formation and cycle
Rocks formation and cycleRocks formation and cycle
Rocks formation and cyclesirrainbow
 
igneousrockppt-160104101353 (1).pptx
igneousrockppt-160104101353 (1).pptxigneousrockppt-160104101353 (1).pptx
igneousrockppt-160104101353 (1).pptxCheyeneReliGlore
 
13. Earth Structure and Rock Cycle_2.pptx
13. Earth Structure and Rock Cycle_2.pptx13. Earth Structure and Rock Cycle_2.pptx
13. Earth Structure and Rock Cycle_2.pptxJomarDeray1
 
ROCKSEARTHSCIENCE
ROCKSEARTHSCIENCEROCKSEARTHSCIENCE
ROCKSEARTHSCIENCErossy212
 
Rocks AND SOIL FORMATION
Rocks AND SOIL FORMATIONRocks AND SOIL FORMATION
Rocks AND SOIL FORMATIONMoses Lutta
 
Engineering Soil Mechanics (Fawzan Fahry)
Engineering Soil Mechanics  (Fawzan Fahry)Engineering Soil Mechanics  (Fawzan Fahry)
Engineering Soil Mechanics (Fawzan Fahry)FAwzan Mohamad
 
Rocks With Miss Gow
Rocks With Miss GowRocks With Miss Gow
Rocks With Miss Gowmeg0001
 
Rocks With Miss Gow
Rocks With Miss GowRocks With Miss Gow
Rocks With Miss Gowmeg0001
 
Rocks With Miss Gow
Rocks With Miss GowRocks With Miss Gow
Rocks With Miss Gowmeg0001
 
Igneous texture & structure Dyuti krushna Jena.pptx
Igneous texture & structure     Dyuti krushna Jena.pptxIgneous texture & structure     Dyuti krushna Jena.pptx
Igneous texture & structure Dyuti krushna Jena.pptxDyutikrushnaJena
 
Igneous rocks
Igneous rocksIgneous rocks
Igneous rocksVasu Goel
 
The Geo-Chemistry of Igneous Rocks
The Geo-Chemistry of Igneous RocksThe Geo-Chemistry of Igneous Rocks
The Geo-Chemistry of Igneous Rocksedlaw
 
Summary of how to classify minerals
Summary of how to classify mineralsSummary of how to classify minerals
Summary of how to classify mineralsDr Robert Craig PhD
 

Similar to Igneous rock ge 106 (20)

Igneous rocks bs 1st year
Igneous rocks  bs 1st yearIgneous rocks  bs 1st year
Igneous rocks bs 1st year
 
NRM_1.pptx
NRM_1.pptxNRM_1.pptx
NRM_1.pptx
 
II.A Minerals and Rocks
II.A Minerals and RocksII.A Minerals and Rocks
II.A Minerals and Rocks
 
Week 4-Rocks.pptx
Week 4-Rocks.pptxWeek 4-Rocks.pptx
Week 4-Rocks.pptx
 
Rocks formation and cycle
Rocks formation and cycleRocks formation and cycle
Rocks formation and cycle
 
igneousrockppt-160104101353 (1).pptx
igneousrockppt-160104101353 (1).pptxigneousrockppt-160104101353 (1).pptx
igneousrockppt-160104101353 (1).pptx
 
Rocks
RocksRocks
Rocks
 
E.g ex 3 igneous rocks (2015-16 )
E.g  ex 3 igneous rocks (2015-16 )E.g  ex 3 igneous rocks (2015-16 )
E.g ex 3 igneous rocks (2015-16 )
 
13. Earth Structure and Rock Cycle_2.pptx
13. Earth Structure and Rock Cycle_2.pptx13. Earth Structure and Rock Cycle_2.pptx
13. Earth Structure and Rock Cycle_2.pptx
 
ROCKSEARTHSCIENCE
ROCKSEARTHSCIENCEROCKSEARTHSCIENCE
ROCKSEARTHSCIENCE
 
Rocks AND SOIL FORMATION
Rocks AND SOIL FORMATIONRocks AND SOIL FORMATION
Rocks AND SOIL FORMATION
 
Engineering Soil Mechanics (Fawzan Fahry)
Engineering Soil Mechanics  (Fawzan Fahry)Engineering Soil Mechanics  (Fawzan Fahry)
Engineering Soil Mechanics (Fawzan Fahry)
 
Rocks With Miss Gow
Rocks With Miss GowRocks With Miss Gow
Rocks With Miss Gow
 
Rocks With Miss Gow
Rocks With Miss GowRocks With Miss Gow
Rocks With Miss Gow
 
Rocks With Miss Gow
Rocks With Miss GowRocks With Miss Gow
Rocks With Miss Gow
 
Igneous texture & structure Dyuti krushna Jena.pptx
Igneous texture & structure     Dyuti krushna Jena.pptxIgneous texture & structure     Dyuti krushna Jena.pptx
Igneous texture & structure Dyuti krushna Jena.pptx
 
Igneous rocks
Igneous rocksIgneous rocks
Igneous rocks
 
The Geo-Chemistry of Igneous Rocks
The Geo-Chemistry of Igneous RocksThe Geo-Chemistry of Igneous Rocks
The Geo-Chemistry of Igneous Rocks
 
Summary of how to classify minerals
Summary of how to classify mineralsSummary of how to classify minerals
Summary of how to classify minerals
 
03.Rocks.ppt
03.Rocks.ppt03.Rocks.ppt
03.Rocks.ppt
 

More from Ahmed Hamza

More from Ahmed Hamza (6)

Nile Delta of Egypt
Nile Delta of EgyptNile Delta of Egypt
Nile Delta of Egypt
 
Mud loggingh (2)
Mud loggingh (2)Mud loggingh (2)
Mud loggingh (2)
 
Fold
FoldFold
Fold
 
Deconvolution
DeconvolutionDeconvolution
Deconvolution
 
Hydro
HydroHydro
Hydro
 
هيدرو
هيدروهيدرو
هيدرو
 

Igneous rock ge 106

  • 2. Igneous Rocks By Moustafa Hashad Three Lectures Lecture - 1 Attendance ??
  • 3. Table of Contents Lecture 1 Lecture 2 What are Rocks?  Major Rock Types  The Rock Cycle  Nature, and Origin of Igneous Rocks  Igneous Rocks  What happens to molten rock as it cools?  Crystal size and Cooling Rates  Texture, Igneous Rock Textures  Phaneritic , Aphanitic , Porphyritic Glassy , Pegmatitc  Pyroclastic Aa Lava, Pahoehoe Lecture 3 Structures of Igneous Rocks. Mineral Composition Magma and Bowen Reaction Series Mineral Composition and Magma Ferromagnesian Silicates Non- Ferromagnesian Silicates Classification of Igneous Rocks. *Color/Texture Igneous Classification **Modal Igneous Classification *** Normative Igneous Classification Igneous Rock Categories Granitic, Basaltic, Andesitic Igneous Rocks Several types of Igneous Rocks: Granite, Rhyolite, Pumice, Obsidian, Gabbro, Basalt, Andesite, Diorite, Tuff.
  • 4. Part 1 and Major Rock Types
  • 5. What are Rocks? Most rocks are an aggregate of one or more minerals and a few rocks are composed of non-mineral matter. There are three major rock types:  1. Igneous  2. Metamorphic  3. Sedimentary 5 Table of Contents
  • 6. Major Rock Types  Igneous rocks are formed by the cooling of molten magma or lava near, at, or below the Earth’s surface.  Sedimentary rocks are formed by the lithification of inorganic and organic sediments deposited near or at the Earth’s surface.  Metamorphic rocks are formed when preexisting rocks are transformed into new rocks by heat and pressure, usually below the Earth’s surface. 6 Table of Contents
  • 7.
  • 8. Major Rock Types Although the three rock Categories are connected in the Endless rock cycle, igneous rocks Are traditionally taught first. Remember details of rock cycle
  • 9. 9 Table of Contents
  • 10. Nature, and Origin of Igneous Rocks
  • 11. Igneous Rocks How to Tell Igneous Rocks  The main thing about Igneous rocks is that they were once hot enough to melt. The following features are all related to that.  Because their mineral grains grew together tightly as the melt cooled, they are relatively strong rocks.  They're made of primary minerals that are mostly black, white or gray. Any other colors they may have are pale.
  • 12. Igneous Rocks Origin of Igneous Rocks The word "igneous" comes from the Latin for fire, and 1- Igneous rocks, in common, have formed by the cooling and crystallization of a melt. 2- This material may have been: a- lava erupted at the Earth's surface, and or b- Magma (un-erupted lava) at depths of up to a few kilometers (shallow magma), or c- Magma in deeper bodies (plutons). Those three different settings create three main types of igneous rocks: 1- Rock formed of lava is called Extrusive Rocks 2- Rock from shallow magma is called Hypabyssal intrusive Rocks and 3- Rock from deep magma is called Plutonic intrusive Rocks The deeper the magma, the slower it cools and the larger the
  • 13. Origin of Igneous Rocks هذه الشريحة و التالية تكرار للشريحة السابقة  Igneous rocks are formed by the cooling of molten rock.  There are two major states of molten rock: Magma and Lava.  Magma is a form of molten rock that exists below the Earth’s surface.  Lava is the term given to magma once it reaches the Earth’s surface, usually in the form of a volcanic eruption.  There are two major classifications of igneous rocks: Intrusive and Extrusive.  Intrusive igneous rocks are formed by magma that cools below the Earth’s surface: a - at shallow depth (Old name Hypabyssal Rocks). And, b - at deep depth .(Old name Plutonic Rocks)  Extrusive igneous rocks are formed by lava that cools at the Earth’s surface. (Old name Volcanic Rocks) 13 Table of Contents
  • 14. Igneous Rocks  Intrusive igneous rocks generally cool very slowly below the earth’s surface or as the magma is rising to the earth’s surface. Hypabyssal Hypabyssal igneous rocks are formed at a depth in between the plutonic and volcanic rocks. These are formed due to cooling and resultant solidification of rising magma just beneath the  earth surface. Hypabyssal rocks are less common than plutonic or volcanic rocks and often form dikes, sills, laccoliths, lopoliths, or phacoliths  Extrusive igneous rocks generally cool quickly when they reach the earth’s surface usually through volcanoes or fissure. 14 Table of Contents
  • 15. Igneous Rocks Igneous rocks form in three main places: 1- where the tectonic plates pull apart (at mid-ocean ridges), 2- where plates come together (at subduction zones) and 3- where continents are pushed together, making the Earth's crust thicker and allowing it to heat to melting.
  • 16. What happens to molten rock as it cools?
  • 17. What happens to molten rock as it cools? 1 - When the temperature of molten rock begins to drop there is a loss of energy that causes ions to slow down. As the ions slow down, they group together and arrange themselves into definit crystalline structures. This process is referred to as crystallization.  So, What is the definition of crystallization ??  Definition:  Crystallization: It is the process where the temperature of molten rock begins to drop, so, there is a loss of energy that causes ions to slow down. As the ions slow down, they group together and arrange themselves into a crystalline structures. 17 Table of Contents
  • 18. What happens to molten rock as it cools? Cont. 2 - During crystallization, the silicon and oxygen atoms are the first to link together forming silicon-oxygen tetrahedrons, which are the building block of all silicate minerals. 3 - As crystallization continues, these individual silicon-oxygen tetrahedrons join with one another, and other ions, to form the basic structure of most minerals and igneous rocks.
  • 19. What happens to molten rock as it cools? Cont. 4 - Environmental conditions including temperature and the presence of water or gases during crystallization affect the composition, the size, and the arrangement of the mineral grains. The size and arrangement of mineral crystals, (usually referred to crystals as grains), define the texture of the rock. So,  Geologists use mineral and textural classifications to infer information about the environmental setting in which different igneous rocks are formed. 19 Table of Contents
  • 20. Crystal size and Cooling Rates
  • 21. Crystal Size and Cooling Rates  Slower cooling rates produce larger individual crystals in the rock  Intrusive igneous rocks generally cool very slowly and tend to have large crystals that produce a course-grained rock. Phaneritic rocks are coarse-grained rocks which contain individual crystals that are relatively even in size and large enough for scientists to identify the different mineral grains that compose the rock. 21 Table of Contents
  • 22. Crystal Size and Cooling Rates  Faster cooling rates produce smaller individual crystals in the rock  Extrusive igneous rocks tend to cool quickly and are characterized by smaller grains that produce a fine-grained rock. Aphanitic is the term used to describe very fine grained rocks. 22 Table of Contents
  • 23. Crystal Size and Cooling Rates- C0nt.  Porphyritic textured rocks contain both a coarse and fine-grained texture.  The coarse grains in a porphyritic rock begin to develop as the magma is cooling below the surface of the earth. Following eruption or exposure to lower temperatures, the remaining magma or lava cools very quickly and forms minerals with fine-grained textures.  As a result, porphyritic textures contain both coarse- and fine–grained minerals. 23 Table of Contents
  • 24. Texture and Igneous Rock Textures
  • 25. Texture Definition: Texture Texture is a term used to describe the size, shape, and arrangement of interlocking crystallized mineral grains in an igneous rock.  Two major factors affect the size of crystal grains in an igneous rock:  1) Rate of cooling at which molten rock cools; Slow …… or ….. fast  2) Amount of dissolved gases or fluids in the magma. 25 Table of Contents
  • 26. Texture Cont.  Igneous minerals vary greatly in grain size. Grain-size classes are similar to the sedimentary scale, but there are fewer divisions with a greater range of size.  Phenocrysts are grains in an igneous rock that are larger than the other grains that make up the rest of the rock. 26 Grain Size Categories Grain Size Divisions fine grained = < 1 mm medium grained = 1 mm < 5 mm coarse grained = 5 mm < 3 cm very coarse-grained = > 3 cm Phenocrysts Texture microphenocrysts = 0.03 mm – 0.3 mm phenocrysts = 0.3 mm – 5 mm megaphenocrysts = > 5 mm Table of Contents
  • 27. Igneous Rock Textures - 1  Phaneritic (Intrusive)  Aphanitic (Extrusive)  Porphyritic (Intrusive and Extrusive)  Glassy (Extrusive) Pegmatitic (Intrusive)  Pyroclastic Materials (Extrusive)  Aa Lava (Extrusive)  Pahoehoe Lava (Extrusive) 27 Table of Contents
  • 28. Phaneritic Texture Phaneritic (Intrusive) Phaneritic rocks are coarse-grained rocks which form below the Earth’s surface. The individual crystals are relatively even-sized and large enough for scientists to identify the different mineral grains that compose the rock. 28 Quartz Crystals: (White) Feldspar Crystals: (Pink) Biotite Crystals: (Black) Granite rock with a phaneritic texture Table of Contents Igneous Rock Textures - 2
  • 29. Aphanitic Texture  Aphanitic (Extrusive)  Definition: Aphanitic rocks are very fine-grained and contain crystals that are too small to distinguish without the aid of a magnifying lens.  Aphanitic rocks are often described by how light or dark the rock appears. Lighter colored aphanitic rocks contain mostly non-ferromagnesian silicate minerals. Darker colored aphanitic rocks contain mostly ferromagnesian silicate minerals. Aphanitic rocks may also contain vesicles of remnant gas that give the rock a vesicular texture. Vesicles form when the rock cools very quickly and preserves the openings formed by the expansion of trapped gas bubbles. 29 Basalt rock with an aphanitic and vesicular texture Table of Contents Igneous Rock Textures - 3
  • 30. Porphyritic Texture  Porphyritic (Intrusive and Extrusive) Definition: Porphyritic rocks contain both coarse- and fine-grained textures indicating different environmental conditions which formed the rock. The coarse grains in a porphyritic rock develop as the magma is cooling below the surface of the earth. The fine-grained component of a porphyriic rocks forms when the magma or lava cools faster. The large coarse-grained crystals are referred to as phenocrysts. The small fine-grained crystals are referred to as groundmass. 30 Rhyolite rock with porphyritic texture containing phenocrysts of olivine and pyroxene and a gabbro groundmass. Table of Contents Igneous Rock Textures - 4
  • 31.
  • 32. Porphyritic Texture Definition: Large crystals called phenocrysts are surrounded by an aphanitic matrix or groundmass.
  • 33.
  • 36. Glassy Texture  Glassy (Extrusive)  Definition: Glassy textured rocks are formed by very rapid cooling of magma. Obsidian rock with a glassy texture and conchoidal Glassy rocks often form from magmas with high silica content that arranges into long chainlike structures before crystallization occurs. These silica chains increase the viscosity of the magma and it once it eventually cools it forms a glassy textured rock. Glassy rocks can be considered amorphous because they have no crystalline structure. fractures  Glassy rocks are classified by the amount of glass contained by the rock:  Glass-bearing: 0-20% glass, Glass-rich: 20-50% glass  Glassy: 50 – 100% glass  Obsidian is a common glassy rock. 36 Table of Contents Igneous Rock Textures - 5
  • 37. Pegmatitic Texture  Pegmatitic (Intrusive) veins extending through rock  Definition: Pegmatitic rocks contain large interlocking crystalline grains > 1-2 centimeter in diameter. Examples of pegmatitic Pegmatites are commonly composed of quartz, feldspar, and mica minerals. Pegmatites form from a combination of hydrothermal and igneous processes; and is dependant on the presence of fluids and volatiles such as water, chlorine, bromine, sulfur, and fluorine. 37 Table of Contents Igneous Rock Textures - 6
  • 38. Pegmatitic Texture Pegmatites form late in the crystallization process when there are a lot of fluids present in the molten rock. The fluids enable individual ions to move around more freely, ultimately bonding to form very large crystals.  Pegmatitic dikes form around the margins of intrusive plutons, or occasionally as veins of rock which extend into the pluton. Examples of pegmatitic veins 38 extending through rock Table of Contents Igneous Rock Textures – 6a
  • 39. Pyroclastic Materials  Pyroclastic (Extrusive) Pyroclastic materials form when individual rock fragments are ejected during a violent volcanic eruption and consolidate into larger rock composites when they deposit on the surface. Tuff rock with pyroclastic material.  Pyroclastic rocks contain at least 75% pyroclastic fragments with the remainder consisting of other inorganic sediments or organic materials.  Pyroclastic rocks contain a mixture of different types of particles that are not cohesively joined by interlocking crystals, but instead are consolidated masses of multiple rock fragments. Tephra is the term used to describe pyroclastic sediments. 39 Table of Contents Igneous Rock Textures - 7
  • 40. Pyroclastic Fragments  Pyroclastic materials do not conform well to igneous grain size classifications. Instead, geologists use the following terms to describe pyroclastic fragments:  Bombs: fragments with a mean diameter > 64 mm, and a rounded shape.  Blocks: fragments with a mean diameter > 64 mm, and a blocky, angular shape.  Lapilli: fragments in any shape with a mean diameter of 2- 64 mm.  Ash: grains of pyroclastic fragments with a mean diameter < 2 mm. This includes coarse ash grains (0.032 -2 mm) and fine ash grains (< 0.032 mm). 40 Table of Contents Igneous Rock Textures - 8
  • 41. Aa 0r aa Lava  Aa Lava (Extrusive)  Aa is a basaltic lava flow that has a rough surface, characterized by sharp and jagged blocks.  Aa flows move slowly (5-50 meters per hour) and are often several meters thick.  As aa lava flows, the outer surface and advancing edge cools first  Aa lava flows are common on the Hawaiian Islands. The aa flows move so slowly that tourists can walk up to them and take pictures. Aa lava in Hawaii’s Volcanoes National Park. 41 Table of Contents Igneous Rock Textures - 9
  • 42. Pahoehoe Lava  Pahoehoe Lava (Extrusive) Pahoehoe (pronounced pah-hoy-hoy) is a basaltic lava flow that has a smooth and twisty, rope-like surface. The characteristic ropy texture forms as the surface lava cools while the molten material beneath it is still moving. The tension formed by the cooling lava causes it to wrinkle as the subsurface lava continues to flow. As a result the surface cools in a series of overlapping, ropy lobes. Pahoehoe lava flows move slow enough (5-50 meters per hour) for observers to watch the cooling lava as it advances forward. 42 Pahoehoe lava flows in Hawaii. Table of Contents Igneous Rock Textures - 10
  • 43. IGNEOUS INTRUSIONS / PLUTONS intrusions/ plutons As magma cools underground, it will begin to solidify within Earth's crust. Once completely crystallized, these masses of igneous intrusive rock are referred to as intrusions or as plutons (after Pluto, Greek god of the underworld). Both terms are used interchangeably by geologists, so take your pick. Dikes - are relatively small igneous intrusions formed as magma penetrates into rock fractures and solidifies into thin, sheet-like bodies. Where dikes are very abundant they are referred to as dike swarms. Three-inch thick dike formed within a larger mass of granite
  • 44. 44