1. Metamorphism Changes in Rock Composition or Texture
Due to Heat, Pressure and Action of Fluids

2. We Do Not Live at “Normal” Conditions
By the standards of Earth’s interior, we live in a frozen vacuum
Things that look “abnormal” to us are normal behavior for materials
Solids can flow
Solids can react chemically with each other
A given material can have several different atomic structures

3. Chemical Changes in Rocks
Weathering
At Surface
Diagenesis
Sedimentary Rocks
Metamorphism
Starts about 200 C
Outside range of normal near-surface conditions

4. Where Does the Heat Come from?
Uranium and Thorium  Other Elements + Lead + Radiation (about 90%) Potassium-40  Calcium-40 or Argon-40 + Radiation (about 10%) Possibly some primordial heat (controversial)

5. Where Does the Pressure Come from?
Air Pressure = 14 P.s.i. (1 Atmosphere or 1 Bar = 100 kPa)
Pressure Beneath 10 Meters (33 Ft.) Of Water = 1 Atm. = 1 Bar
Same Pressure Beneath 3.5 m (10 ft.) Of Rock
Pressure in Deepest Part of Ocean = 1000 Bars
Pressure under One Mile of Rock = 500 Bars
1000 Bars (2 Mi. or 3.5 km Of Rock) = 1 Kilobar (Kb.) = 100 MPa

6. Pressure Units 1 Newton (N) = gravitational attraction on 100 grams
One Newton = 7 Fig Newtons
1 Pascal (Pa) = 1 N/square meter
1 Pascal = pressure under thin cardboard or 0.1 mm water
A Thin section exerts about 1 Pa pressure on the slide
One bar = 1 atm = 100 kPa
1 MPa = 10 bars
1 GPa = 10 kilobars

7. Types of Metamorphism Contact Around Intrusions or Local Heat Sources
Regional
Usually Accompanied by Deformation
Cataclasis
Shearing and fault zones
Shock
Ultra-high pressures and rapid deformation

8. What Happens During Metamorphism
Minerals React to Form New Minerals
2SiO2 + CaMg(CO3) 2 == CaMgSi2O6 + 2CO2
Quartz + Dolomite == Pyroxene
Minerals Change Form
Al2SiO5 == Al2SiO5
Andalusite == Kyanite
New Materials Are Added (Metasomatism)
CaMg(SiO2)2 + 2CO2 == CaMg(CO3)2 + 2SiO2
Pyroxene + CO2 == Dolomite + Quartz
Minerals in Solution == Ore Bodies
Recrystallization
Cataclasis
Shock Metamorphism

9. Polymorphism Al2SiO5 Andalusite Kyanite Sillimanite
Ice - 6 high pressure forms
Diamond - Graphite
Calcite - Aragonite
Quartz -
- Tridymite - Cristobalite (increasing temperature)
- Coesite - Stishovite (increasing pressure)

10. Why Don't Rocks "De-metamorphose"?
Reactions Can't Reverse Because Ingredients Lost
2AlSi2O5(OH) == Al2SiO5 + 3SiO2 + H2O
Clay Mineral == Andalusite + Quartz + Water (Lost)
An example of carbonate metamorphism:
CaMg(CO3) 2 + 2SiO2 == CaMgSi2O6 +2CO2
Dolomite + Quartz == Pyroxene + CO2 (Lost)
Reactions "Freeze"
Sometimes it Does Happen if Fluids Present
Retrograde Metamorphism
On the surface we call it weathering

11. Foliation
Foliation is a sheetlike structure that forms when rocks are deformed.

12. Foliation Flattening Grain Rotation Solution New Minerals
Partial Melting
Shearing

13. Foliation In every case, the foliation is:
In the direction of least resistance
at right angles to the direction of greatest compression.

14. Metamorphic Grade - Degree to Which the Rock Has Changed Composition
Can Often See Original Bedding
Can Sometimes Even See Deformed Fossils
At High Grades, Rocks Can Often Lose All Trace of Their Original Appearance

15. 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
Greenstone
800
Quartzite
Phyllite
Biotite
900
Schist
Garnet
1000
Amphibolite
Staurolite
1100
Gneiss
Kyanite
1200
Sillimanite
Melting Begins

17. 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
Greenstone
800
Quartzite
Phyllite
Biotite
900
Schist
Garnet
1000
Amphibolite
Staurolite
1100
Gneiss
Kyanite
1200
Sillimanite
Melting Begins

19. 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
Greenstone
800
Quartzite
Phyllite
Biotite
900
Schist
Garnet
1000
Amphibolite
Staurolite
1100
Gneiss
Kyanite
1200
Sillimanite
Melting Begins

21. 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
Greenstone
800
Quartzite
Phyllite
Biotite
900
Schist
Garnet
1000
Amphibolite
Staurolite
1100
Gneiss
Kyanite
1200
Sillimanite
Melting Begins

23. 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
Greenstone
800
Quartzite
Phyllite
Biotite
900
Schist
Garnet
1000
Amphibolite
Staurolite
1100
Gneiss
Kyanite
1200
Sillimanite
Melting Begins

25. What About Other Rocks?

26. Metamorphic Facies Depth\Temp 300C 400C 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
Gneiss
Granulite Sillimanite forms Muscovite breaks down to K-feldspar Partial Melting
15 km
Blueschist
20 km - 6 kb
25 km
30 km - 9 kb
35 km
40 km - 12 kb
Not Found
Eclogite (Mantle)

27. Metamorphic Map

28. Mantle Rocks

29. Metamorphism and Plate Tectonics