02 Igneous
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Transcript of 02 Igneous
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Igneous Rocks
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Igneous Rocks
Ignis means fire
Rocks that are formed from cystallization
of magma
Magmais molten rock
Lavais magma that is on the Earths Surface
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Igneous Rocks
Two Types of Igneous Rocks
Extrusive (Exterior)
Intrusive (Interior)
Igneous rocks that solidify into rock beneath
Earths surface
Coarse Grained
Cool Slowly
Granite
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Extrusive Igneous Rocks
Extrusive (Exterior)
Igneous rocks that
solidify into rock onEarths surface
Fine Grained
Cool Quickly
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Intrusive Igneous Rocks
Intrusive (Interior)
Igneous rocks that
solidify into rockbeneath Earths
surface
Coarse Grained
Cool Slowly
Granite
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Igneous Rock Formation
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Origin of Magma
Where does the heat
come from that melts
rocks? Formation of Earth
Heat from the decay of
radioactive elements
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Factors that Affect Magma
Formation Temperature
Increases with depth
Pressure Increases with depth
Water Content
Decreases meltingpoint
Mineral Composition
Different minerals,
different melting points
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Characteristics of Magma
Slushy Mix of molten rock,gases, and mineral crystals
Common Elements
Oxygen (O) Silicon (Si)
Aluminum (Al)
Iron (Fe)
Magnesium (Mg)
Calcium (Ca)
Potassium (K)
Sodium (Na)
Compounds in Magma Silica ( Si02)
Most abundant
Greatest effect on MagmaCharacteristics
Effects melting temp
Viscosity of Magma
Types of Magma Based on amount of Silica
Basaltic Andesitic
Rhyolitic
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Type of Magma SiO2 Content
Rhyolitic 70%
Andesitic 60%
Basaltic 50%
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Melting Rocks
Question
Does a rocks melt like an ice cube, all at the
same time?
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Melting Rocks
Rocks melt according to their melting points.
Example: Ice cube with wax
Which would melt first ice or wax?
This example is known as partial melting.
Partial Melting: some minerals melt at lower
temperatures and other minerals remain solid
Think of stew
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Fractional Crystallization
Opposite of Partial Melting
Last to melt are first to solidify (crystallize)
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Bowens Reaction Series
N.L. Bowen
Canadian
1900s
Stated that as magma cools, minerals form in
predictable patterns
Known as Bowens Reaction Series
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Bowens Reaction Series
Two Branches
Feldspars
Continuous, gradual change of mineralcompositions
Iron-Rich Minerals
An abrupt change of mineral type
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Bowens Reaction Series
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Feldspars
Continuous Change
First Feldspars are
rich in Calcium (Ca) Sodium (Na)
increases as cooling
continues
Last Feldspars to
form are Sodium rich
(Na)
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Iron Rich Minerals
Discontinuous Change
Magnesium (Mg) cools around18000C, when olivinecrystallizes, this continous up
to 15570C. Now Pyroxene begins to form.
All olivine that was formed isnow turned to pyroxene
Quartz is the last to form,because silica and oxygen are
the last to crystallize
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Why do we find Olivine?
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Four main groups of igneous rocks based on
magma type/mineral composition
Felsic: high silica content, light colored, from thick & slow movingmagma, contains low amounts of Ca, Fe, and Mg dominant mineralsquartz, potassium rich feldspar Ex: granite, pumice, rhyolite
Magma Type:
Intermediate: moderate amount of silica, mixture of colors dominantminerals: sodium and calcium rich feldspar Ex: andesite, diorite
Magma Type:
Mafic: low silica content, dark colored, high levels of Fe & Mg formed fromthinner, more fluid, & hotter magma than Felsic rocks dominant mineralshornblende, calcium rich feldspar Ex: basalt, gabbro Magma Type:
Ultramafic: very low silica content, dark colors, high levels of Fe & Mgdominant minerals: olivine, pyroxene Ex: peridotite, dunite
Magma Type:
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Classifying Igneous Rocks
Igneous rock textures:
Crystal size is dictated by the rate of cooling of the
magma body. A slower cooling rate results in largermineral crystals being formed in the rocks as they
cool.
Porphyritic texture -Large crystals surrounded by
fine grained rock. The rock initially cools slowly to
form some large crystals and then cools quickly to
form the fine grained rock surrounding them.
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The Scheme for
Igneous RockIdentification
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A Brief Tour
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Crystal size
Description
Grain Size
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Igneous rocks have
Intergrown Crystals
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Intergrown
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Intergrown
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Intergrown
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Not Intergrown
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Where it was formedOutside the volcano: Extrusive
Inside the Earth: Intrusive
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Bubbles? Yes= Vesicular
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Bubbles? No=Non-vesicular
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ColorVery Light
Light
NotVery Light Not Very Dark
Dark
Very Dark
Neither Light nor Dark
Lightest
Darkes
t
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DensityVery Light
Light DenseVery Dense
Medium Density
Fi di Th Mi l
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Finding The MineralsIdentify the rock. Unless you have other information,
work in the middle of the rocks box.
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This is the amount of Potassium Feldspar in the rock.
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This is the amount of Quartz in the rock.
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This is the amount of Plagioclase Feldspar in the rock.
Use tick marks on a scrap paper to measure the percentage
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Use tick marks on a scrap paper to measure the percentage.
Potassium Feldspar 25%
Quartz 40%
Name a light colored fine grained
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PracticeName a light-colored, fine-grained
rock with no bubbles.
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Name a coarse-grained, dense rock.
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Igneous Rock Resources
Ore Deposits
Building Materials
Other Uses
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Ore Deposits Veins: streaks of valuable metal within a
mineral. Created when a metal-rich fluid, suchas gold-quartz, goes through fractionalcrystallization, the mineral (quartz) has a lowercrystallization temp and thus solidifies before
the gold. The gold remains liquid and settlesbetween the quartz crystals forming goldveins.
Pegmatites: veins with extremely large graincrystals. Creates some of the worlds most
precious gems. Kimberlites: intrusions of magma cooled deep
within earths crust. Usually find diamondswith kimberlites. Named after location of firstdiscovery, Kimberly, South Africa.
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Building Materials
Many IRs are used in building materials
because of their interlocking crystals
strength IRs are fairly weather resistant
Ex: Granitebuilding
Ex: Basaltcrushed up to make gravel
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Other Uses
Pumicecleaning and polishes
Obsidian
heated to make perlite, a soil additive thatkeeps soil loose.
scalpelsmore precise and smoother than
steel, but 10x the cost