Metamorphism

Steven Dutch, Professor Emeritus, Natural and Applied Sciences, University of Wisconsin - Green Bay


Metamorphism

Where Does the Heat Come from?

Where Does the Pressure Come from?

1000 Bars (2 Mi. or 3 km Of Rock) = 1 Kilobar (Kb.)


Metamorphic Rocks Form Many Km below the Surface
How Do They Get to the Surface?


Types of Metamorphism

Contact

Regional


What Happens During Metamorphism

Minerals React to Form New Minerals

Minerals Change Form

New Materials Are Added (Metasomatism)

Recrystallization


Why Don't Rocks "De-metamorphose"?


Grade - Degree to Which the Rock Has Changed Composition


Major Metamorphic Rock Types

Temp C Temp F Coal Limestone Sandstone Basalt Shale Index Minerals
    Lignite
Bituminous
         
  500 Anthracite          
300 600 Graphite Marble     Slate Chlorite
  700     Quartzite      
  800       Greenstone Phyllite Biotite
500 900         Schist Garnet
  1000       Amphibolite   Staurolite
600 1100         Gneiss Kyanite
  1200           Sillimanite
700             Melting Begins

polymorphism

Metamorphic Facies

Not all changes in rocks are metamorphism:

Depth\Temp 300 C 400 C 500 C 600 C 700 C 800 C
5 km Zeolite Contact Metamorphism - Andalusite forms
10 km - 3 kb Greenschist
Chlorite, Biotite form
  • Slate
  • Greenstone
  • Quartzite
  • Marble
Amphibolite
Garnet, Staurolite, Kyanite form
  • Schist
  • Amphibolite
  • Quartzite
  • Marble
  • Gneiss
Granulite
Sillimanite forms
Muscovite breaks down to K-feldspar
Partial Melting
  • Gneiss
15 km Blueschist
20 km - 6 kb
25 km
30 km - 9 kb
35 km
40 km - 12 kb     Eclogite (Mantle)

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Created March 5, 1997; Last Update November 10, 1998