CH. 3 – IGNEOUS ROCKS
Igneous RocksIgnis = “fire”Form from cooling & crystallization  of magma (molten rock)Lava = molten rock at surface
Igneous RocksClassified by texture & compositionTexture = crystal size of mineralsComposition = minerals present
Changes of State of MatterAdd heat (melting):Rx       Magma (atoms faster)Remove heat (crystallize):Rx (atoms slower)     ...
Texture of Igneous RocksDepends on magma’s cooling rate1) Cools slowlyAtoms can move through liquid   - crystals grow (lar...
Magma’s Cooling Rate2) Cools quicklyForms a solid faster than atoms can move around - crystals are (large, small)
Texture (Crystal Size)Two environments where magma cools:1) At surface or shallow burial2) Deep underground
Types of Texture1) Aphanitic   - crystals invisible to naked eye   - magma cooled ___________   - extrusive/volcanic
Types of Texture2) Vesicular- aphanitic rock w/many holes  (vesicles) in it- gas trapped as magma cools  very quick
Types of Texture3) Phaneritic - crystals easily visible - magma cooled ___________ - intrusive/plutonic
Types of Texture4) Porphyritic - two size crystals in same rockLarge crystals = phenocrystsSmall crystals = groundmass
Porphyritic Texture2-stage cooling process:1st stage = slow cooling at depth_______________ are formed2nd stage = rapid co...
Types of Texture5) Glassy - no crystalline structureEx: Obsidian; pumice
Types of Texture6) PegmaticAll minerals larger than 1 cmForms during later stage of  crystallization- large percentage of ...
Types of Texture7) Pyroclastic“pyro” = fire; “clastic” = piecesConsolidated rock fragments  ejected during violent volcani...
Pyroclastic textureFragments can be volcanic ash,  blobs of magma, or angular  blocks- not composed of interlocking  cryst...
Igneous Rock CompositionThe most abundant elements of  Earth’s crust are _____ &  ______Magma is mostly silica with  varyi...
CompositionOther elements collect in water at  top of magma chamberCreates hydrothermal solution- cools in fractures as hi...
Igneous CompositionsMafic- 45-50% silica (“silica-poor”)- rich in magnesium, iron (Fe), &  calcium- dark-colored: black, d...
Igneous CompositionsFelsic (feldspar & silica)- 60-75% silica (“silica rich”)- rich in aluminum, potassium, &  sodium- lig...
Igneous CompositionsIntermediateAphanitic: medium grayPhaneritic: black & white crystals
Importance of Igneous RocksCompose 90% of Earth’s crustTwo types of crust: oceanic crust = basalt continental crust = gran...
Question:Why different igneous rock compositions if only 8 elements?N.L. Bowen experimented with mafic magmas
Results:** Same sequence of minerals  crystallized from magmaReferred to as Bowen’s Reaction  Series (Fig. 3.16)
Bowen’s Reaction SeriesDiscontinuous series (left) vs.  continuous series (right)Discontinuous series:- each mineral has a...
Continuous seriesDifferent compositions of  plagioclase feldspars- ions of Ca2+ and Na+ can  interchange within crystallin...
Bowen’s Reaction SeriesAs magma crystallizes:First mineral to form = maficComposition of remaining magma changes
Bowen’s Reaction SeriesBiotite uses last mafic elements in  magma- remaining magma becomes  more “silica rich”
Bowen’s Reaction SeriesMinerals that form in same temp. conditions are found together in same igneous rockQUESTION: Which ...
Phenocryst Mineral:a) Quartzb) Potassium feldsparc) Biotited) Calcium-rich plagioclase f-spare) Sodium-rich plagioclase f-...
Felsic magmaFelsic minerals melt at cooler  temp’s- magma not as hot as mafic  magma- felsic magma not as buoyant
Felsic magmaMagma doesn’t reach surfaceEx: Continental crust = granite
Important ConceptsA mineral is stable if the environmental conditions are similar to where it formedEx: temperature, press...
Example:Mafic minerals are stable in ____ temperaturesFelsic minerals are stable in ____ temperatures
Important ConceptsIf a mineral is put under different  environmental conditions, it  becomes unstable- mineral has to reac...
New EnvironmentalConditions:If at the surface, weathering  occursIf within the crust, metamorphism  occurs
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EASC 116 Ch. 3 Igneous Rx

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EASC 116 Ch. 3 Igneous Rx

  1. 1. CH. 3 – IGNEOUS ROCKS
  2. 2. Igneous RocksIgnis = “fire”Form from cooling & crystallization of magma (molten rock)Lava = molten rock at surface
  3. 3. Igneous RocksClassified by texture & compositionTexture = crystal size of mineralsComposition = minerals present
  4. 4. Changes of State of MatterAdd heat (melting):Rx Magma (atoms faster)Remove heat (crystallize):Rx (atoms slower) Magma
  5. 5. Texture of Igneous RocksDepends on magma’s cooling rate1) Cools slowlyAtoms can move through liquid - crystals grow (large, small)
  6. 6. Magma’s Cooling Rate2) Cools quicklyForms a solid faster than atoms can move around - crystals are (large, small)
  7. 7. Texture (Crystal Size)Two environments where magma cools:1) At surface or shallow burial2) Deep underground
  8. 8. Types of Texture1) Aphanitic - crystals invisible to naked eye - magma cooled ___________ - extrusive/volcanic
  9. 9. Types of Texture2) Vesicular- aphanitic rock w/many holes (vesicles) in it- gas trapped as magma cools very quick
  10. 10. Types of Texture3) Phaneritic - crystals easily visible - magma cooled ___________ - intrusive/plutonic
  11. 11. Types of Texture4) Porphyritic - two size crystals in same rockLarge crystals = phenocrystsSmall crystals = groundmass
  12. 12. Porphyritic Texture2-stage cooling process:1st stage = slow cooling at depth_______________ are formed2nd stage = rapid cooling of remaining magma_______________ are formed
  13. 13. Types of Texture5) Glassy - no crystalline structureEx: Obsidian; pumice
  14. 14. Types of Texture6) PegmaticAll minerals larger than 1 cmForms during later stage of crystallization- large percentage of liquid allows ions to migrate easier
  15. 15. Types of Texture7) Pyroclastic“pyro” = fire; “clastic” = piecesConsolidated rock fragments ejected during violent volcanic eruptions
  16. 16. Pyroclastic textureFragments can be volcanic ash, blobs of magma, or angular blocks- not composed of interlocking crystals!
  17. 17. Igneous Rock CompositionThe most abundant elements of Earth’s crust are _____ & ______Magma is mostly silica with varying amounts of other six elements
  18. 18. CompositionOther elements collect in water at top of magma chamberCreates hydrothermal solution- cools in fractures as highly concentrated ore deposits
  19. 19. Igneous CompositionsMafic- 45-50% silica (“silica-poor”)- rich in magnesium, iron (Fe), & calcium- dark-colored: black, dark gray, brownish-red
  20. 20. Igneous CompositionsFelsic (feldspar & silica)- 60-75% silica (“silica rich”)- rich in aluminum, potassium, & sodium- light-colored: light gray, pinkish
  21. 21. Igneous CompositionsIntermediateAphanitic: medium grayPhaneritic: black & white crystals
  22. 22. Importance of Igneous RocksCompose 90% of Earth’s crustTwo types of crust: oceanic crust = basalt continental crust = granite
  23. 23. Question:Why different igneous rock compositions if only 8 elements?N.L. Bowen experimented with mafic magmas
  24. 24. Results:** Same sequence of minerals crystallized from magmaReferred to as Bowen’s Reaction Series (Fig. 3.16)
  25. 25. Bowen’s Reaction SeriesDiscontinuous series (left) vs. continuous series (right)Discontinuous series:- each mineral has a unique silicate structure
  26. 26. Continuous seriesDifferent compositions of plagioclase feldspars- ions of Ca2+ and Na+ can interchange within crystalline structure
  27. 27. Bowen’s Reaction SeriesAs magma crystallizes:First mineral to form = maficComposition of remaining magma changes
  28. 28. Bowen’s Reaction SeriesBiotite uses last mafic elements in magma- remaining magma becomes more “silica rich”
  29. 29. Bowen’s Reaction SeriesMinerals that form in same temp. conditions are found together in same igneous rockQUESTION: Which mineral would you expect to form phenocrysts in a porphyritic basalt?
  30. 30. Phenocryst Mineral:a) Quartzb) Potassium feldsparc) Biotited) Calcium-rich plagioclase f-spare) Sodium-rich plagioclase f-spar
  31. 31. Felsic magmaFelsic minerals melt at cooler temp’s- magma not as hot as mafic magma- felsic magma not as buoyant
  32. 32. Felsic magmaMagma doesn’t reach surfaceEx: Continental crust = granite
  33. 33. Important ConceptsA mineral is stable if the environmental conditions are similar to where it formedEx: temperature, pressure, water- content
  34. 34. Example:Mafic minerals are stable in ____ temperaturesFelsic minerals are stable in ____ temperatures
  35. 35. Important ConceptsIf a mineral is put under different environmental conditions, it becomes unstable- mineral has to react to new environment by changing
  36. 36. New EnvironmentalConditions:If at the surface, weathering occursIf within the crust, metamorphism occurs

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