1. Our Geologic Environment
Rocks

2. Metamorphic Rocks

3. Metamorphism Igneous rocks Sedimentary rocks Other metamorphic rocks
The transition of one rock into another by temperatures and/or pressures unlike those in which it formed
Metamorphic rocks are produced from
Igneous rocks
Sedimentary rocks
Other metamorphic rocks

4. Metamorphic rocks“changed form”
How?
Increased pressure
Increased temperature
Fluids  chemical reactions
Back under the microscope

5. Contact Metamorphism

10. Metamorphic Progression (Pressure Dominating)
Shale
Slate
Phyllite
Gneiss
Schist

11. Foliation = Layering
Under the microscope
Schist - foliated

12. The Origin of Foliation
Geostatic
Pressure
Differential
Stress
Regional
Metamorphism
Burial
Metamorphism

13. Foliation can be very easy to recognize (and interpret)
What direction did maximum compression act on the sample on the right?

16. Other metamorphic rocks are not so easy to recognize… Sandstone  Quartzite
Grains are interlocking
Grains are separate

17. Limestone Marble Limestone… Marble… Large, reflective crystals
small dull-looking rock…

18. Gneiss
Granite

19. Morton Gneiss

20. Slate
Shale

22. Normal crust Geothermal gradient (25 C/km)
Metamorphism increases with both pressure and temperature
Normal crust Geothermal gradient (25 C/km)
shale
slate 10
phyllite
Depth (km) 20
schist
Melt 30
gneiss
200
400
600
800
Temperature (C)

23. Metamorphic Additions
Chlorite: Green
Increasing
Meta’ism
Biotite: Black Flakes
Amphibole: Black Needles
Garnet: “fake rubies”
Kyanite: Blue blades