Igneous Rocks

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Igneous Rocks
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Igneous Rocks are rocks that Crystallize from a
Magma.
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Crystallization
The formation of minerals. Igneous
Crystallization Freezing, Solidifying from
Magma.
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Magma
Molten Rock Below surface Magma On surface -
Lava
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Intrusive Coarse Grained,
Form in the Earth Plutons
Extrusive Fine Grained, Form at or near
the surface, Volcanic
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Intrusive Rock Form in warm environment Slower
crystallization Time to grow large
grains Extrusive Rock Form in cold
environment Faster crystallization Less time,
only small grains form
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Plate Tectonics Diagram on Board
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Classification of Igneous Rocks by grain size and
composition
Felsic Intermediate
Mafic Granite Diorite
Gabbro Rhyolite Andesite
Basalt Quartz Feldspar
Olivine Feldspars Amphibols
Pyroxene Muscovit Biotite
Feldspar Si, Al
Fe, Mg
Coarse Intrusive Fine Extrusive
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Classification of Igneous Rocks by grain size and
composition
Felsic Intermediate
Mafic Granite Diorite
Gabbro Rhyolite Andesite
Basalt
Coarse Intrusive Fine Extrusive
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Classification of Igneous Rocks by grain size and
composition
Felsic Intermediate
Mafic Granite Diorite
Gabbro Rhyolite Andesite
Basalt Quartz Feldspar
Olivine Feldspars Amphibols
Pyroxene Muscovite Biotite
Feldspar Si, Al
Fe, Mg
Coarse Intrusive Fine Extrusive
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Bowens Reaction Series
Ca Rich
Olivine Pyroxene Amphibols
Biotite
High Temps Low Temps
Plagioclase Feldspar
Na Rich
Orthoclase Feldspar Quartz Muscovite
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Classification of Igneous Rocks by grain size and
composition
Felsic Intermediate
Mafic Granite Diorite
Gabbro Rhyolite Andesite
Basalt Quartz Feldspar
Olivine Feldspars Amphibols
Pyroxene Muscovite Biotite
Feldspar Si, Al
Fe, Mg
Coarse Intrusive Fine Extrusive
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Microphotographs of Igneous Rocks
Gabbro
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Basalt
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Intrusive Bodies Batholith
Stock gt 1 km lt 1 km
Surface
Intrusion
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Intrusive Bodies Dike - discordant
Sill - concordant
Surface
Dike
Sill
Intrusion
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Mafic Dikes
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GRANITE is an Intrusive Rock (forms below
surface) Why do we see so much GRANITE at the
surface ?
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Surface
Intrusion
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Millions of Years of Weathering and Erosion
Surface
Intrusion
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Granite exposed on the Surface
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Enchanted Rock State Park, Texas
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Photo and Illustration Credits

• 1, 5 Unknown
• Tarbuck and Lutgens,
  Earth, Prentice Hall
• 3, 4 microscopy and
  mineral images
• users.skynet.be/jm-derochette/index
• Npolar.no/geonet/picture_
  atlas
• 7 Texas Film
  Commission website