METAMORPHIC ROCKS

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METAMORPHIC ROCKS
Rocks that form from other pre-existing rock
(sedimentary, igneous, or metamorphic) that have
been changed from high temperature and/or high
pressure
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Metamorphic Rocks
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Metamorphic Rocks Formation
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Conditions that cause rock to undergo
metamorphism include

• Heat - Under conditions of high temperature from
  magma contacting pre-existing rock.

• Pressure - Deep burial and pressure from
  mountain formation.

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Types of Metamorphism
1. Contact Metamorphism
2. Regional Metamorphism
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Contact Metamorphism

• Deep burial and pressure from mountain formation.
• The main metamorphic agent is heat.
• Also forms when pre-existing rock comes into
  contact with molten lava or magma. The heat from
  the molten material is hot enough to cause the
  minerals in the original rock to re-crystallize,
  but not melt.

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Regional Metamorphism

• Covers large areas typically associated with
  mountains
• Deep burial and pressure from mountain formation.
• Heat and Pressure change the rock

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Types of Metamorphic Rocks

• Foliated rocks with mineral crystals arranged in
  cable-like distorted layers/structures
• Mineral Alignment
• Banding
• Animation Foliation
• Nonfoliated rocks with recrystallized minerals
  no layering
• Recrystallization This is the growth of new
  mineral crystals from other rocks.

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Scheme for Metamorphic Rock Identification
Texture Texture Composition Type of Metamorphism Comment Rock Name
Mica Regional (Heat and Pressure increase w/ depth) Low-Grade metamorphism of SHALE
Mica, Quartz, Feldspar, Amphiboles, Garnet Regional (Heat and Pressure increase w/ depth) Foliation surfaces shiny from microscopic mica crystals
Mica, Quartz, Feldspar, Amphiboles, Garnet, Pyroxene Regional (Heat and Pressure increase w/ depth) Platy mica crystals visible
Mica, Quartz, Feldspar, Amphiboles, Garnet, Pyroxene Regional (Heat and Pressure increase w/ depth) Compact, may split easily
Slate
Phyllite
MINERAL ALIGNMENT
FOLIATED
Schist
BAND- ING
Gneiss
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Progression of Metamorphism
Start with a shale and then hit it with heat and
pressure!
Rock Name Rock Type Grade of Metamorphism
Shale Sedimentary -----
Slate Metamorphic Low
Phyllite Metamorphic Low/Intermediate
Schist Metamorphic Intermediate/High
Gneiss Metamorphic High
Molten Rock Cools into Igneous Rock -----
More Heat Pressure
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Shale (Sedimentary Rock)
Heat Pressure
Slate (Metamorphic Rock)
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Slate (Metamorphic Rock)
Heat Pressure
Phyllite (Metamorphic Rock)
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Phyllite (Metamorphic Rock)
Heat Pressure
Schist (Metamorphic Rock)
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With even more heat pressure(High-Grade
Metamorphism)
you end up with something that is really
Gneiss!
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Scheme for Metamorphic Rock Identification
Texture Composition Type of Metamorphism Comment Rock Name
Variable Contact (Heat) Various rocks changed by nearby magma/lava
Quartz Metamorphism of Quartz
Calcite and/or Dolomite Metamorphism of
Various minerals in particles and matrix Pebbles may be distorted or stretched
Hornfels
Quartzite
Sandstone
Regional (Heat Pressure)
NONFOLIATED
Limestone or Dolostone
Marble
Metaconglomerate
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• ESRT p. 7
• Animation Metamorphic Rock Scheme

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Where are metamorphic rocks found?

• At the interface between igneous and sedimentary
  rocks

• Mountainous regions

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THE ROCK CYCLE

• How are rocks classified?

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How are rocks classified?

• By their origin (the way they are formed)

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Major Rock Groups

• Sedimentary
• Formed at the Earths surface
• Clastic (Mineral Fragments or grains, clays)
• Crystalline (chemical precipitates and
  evaporites)
• Bioclastic (formed organically from shells or
  plants)
• Igneous
• Formed from magma (molten rock)
• Plutonic (intrusive)slow cooling, coarse/very
  coarse crystals
• Volcanic (extrusion) quick cooling at the
  surface, glassy/fine crystals
• Metamorphic
• Changed by heat and pressure

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Rock Cycle Conclusion
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Fig. 2.9
MAGMA
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IGNEOUS
Solidification
MAGMA
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IGNEOUS Plutonic
Solidification
MAGMA
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Volcanic IGNEOUS Plutonic
Solidification
MAGMA
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Weathering Erosion
Uplift
Volcanic IGNEOUS Plutonic
Solidification
MAGMA
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SEDIMENT
SEDIMENT
Weathering Erosion
Volcanic IGNEOUS Plutonic
Solidification
MAGMA
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Erosion
SEDIMENT
Weathering Erosion
Transport
Deposition
Volcanic IGNEOUS Plutonic
SEDIMENTARY
Solidification
MAGMA
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Deposition
SEDIMENT
Weathering Erosion
Burial/Compaction
Cementation
Volcanic IGNEOUS Plutonic
SEDIMENTARY
Solidification
MAGMA
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Deposition
SEDIMENT
Weathering Erosion
Burial/Compaction
Cementation
Volcanic IGNEOUS Plutonic
SEDIMENTARY
Increased PT
METAMORPHIC
Solidification
MAGMA
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Deposition
SEDIMENT
Weathering Erosion
Burial/Compaction
Cementation
Volcanic IGNEOUS Plutonic
Can you see any shortcuts?
SEDIMENTARY
Increased PT
METAMORPHIC
Solidification
Melting
MAGMA
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Deposition
SEDIMENT
Weathering Erosion
Burial/Compaction
Cementation
Volcanic IGNEOUS Plutonic
SEDIMENTARY
Increased PT
METAMORPHIC
Solidification
Melting
MAGMA
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Deposition
SEDIMENT
Weathering Erosion
Burial/Compaction
Cementation
Volcanic IGNEOUS Plutonic
SEDIMENTARY
Increased PT
METAMORPHIC
Solidification
Melting
MAGMA
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Citations

• Slide 6 (Progression of Metamorphism of Shale)
• http//physics.uwstout.edu/geo/_derived/sect4.htm
  _txt_sect4.2.gif
• Slide 10
• Shale
• http//library.thinkquest.org/06aug/02459/rocks/se
  dimentary/Shale.jpg
• Slate
• http//www.global-b2b-network.com/direct/dbimage/
  10260661/Grey_Slate.jpg
• Slide 11
• Phyllite
• http//www.bedford.k12.ny.us/flhs/science/geoscien
  ce/images/phyllite.jpg
• Slide 12
• Schist (1)
• http//www.randall.k12.wi.us/rocks/images/schist-w
  ith-garnet.jpg
• Schist (2)
• http//www.es.ucl.ac.uk/schools/Glossary/schist.jp
  g
• Slide 13
• Gneiss (1)
• http//hyperphysics.phy-astr.gsu.edu/hbase/geophys
  /geopic/gneiss2.jpg
• Gneiss (2)