1. John Grotzinger, Thomas H. Jordan,
Frank Press, Raymond Siever,
Understanding Earth
Fifth Edition
Chapter 6:
Metamorphic Rocks
Copyright © 2007 by W. H. Freeman & Company

2. Concepts you will need to know for the exams CHAPTER 6
METAMORPHIC ROCKS
Controls on metamorphism by: P,T, fluids
Isotherm
Geothermal gradient
Confining pressure
Directed pressure
Regional metamorphism
Contact metamorphism
High-P metamorphism
Burial or low-grade metamorphism
Foliated texture
Crystal Growth
Pressure-Temperature Paths (pro-grade and retrograde metamorphism)

4. Factors that control the type and and degree Metamorphism
Heat
Pressure
Fluids

5. Temperature increases with depth A typical continental geothermal gradient is 30 degrees C per kilometer
Where is the 1300 degree isotherm?
Old lithosphere km
New lithosphere (Divergent) - 30 km
Volcanic regions (Convergent)- 50 km

11. Confining Pressure
Confining pressure is the same in all directions (incl. 3rd dimension)
In water, that is
one ton per m2 each meter of depth
10 m ~ 1 atm or 10 tons of pressure

12. Directed Pressure
When one pressure is greater than the other three (incl. 3rd dimension)
If directed pressure is great enough rocks can break and/or fold

13. Fluids Accelerate chemical reactions
Dissolve ions and move them from one mineral to another
(A change in rock composition by fluid transport is metasomatism)

16. TYPES OF METAMORPHISM Pressure (Impacts) Subduction Zones
Regional Metamorphism
Increasing grade
Burial
(low-P, low-T),
low-grade
Mountain belts
Contact
Fluids
metasomatism)
Temperature

17. shock, contact, regional, and burial
Types of metamorphism
shock, contact, regional, and burial

18. Shock metamorphism Regional metamorphism Depth, km Oceanic crust 3535
Continental crust
Oceanic
lithosphere 75
Continental mantle lithosphere
Asthenosphere

19. Shock metamorphism Regional metamorphism Regional metamorphism Depth,
Oceanic
crust 35
Continental crust
Oceanic
lithosphere 75
Continental mantle lithosphere
Asthenosphere

20. Regional high-pressure metamorphism Shock metamorphism Regional
Depth, km
Oceanic
crust 35
Continental crust
Oceanic
lithosphere 75
Continental mantle lithosphere
Asthenosphere

21. Regional high-pressure metamorphism Shock metamorphism Regional
Contact
metamorphism
Regional
metamorphism
Depth, km
Oceanic
crust 35
Continental crust
Oceanic
lithosphere 75
Continental mantle lithosphere
Asthenosphere

22. Regional high-pressure metamorphism Shock metamorphism Regional
Contact
metamorphism
Regional
metamorphism
Depth, km
Oceanic
crust 35
Continental crust
Oceanic
lithosphere 75
Continental mantle lithosphere
Asthenosphere

23. Regional high-pressure metamorphism Shock metamorphism Regional
Contact
metamorphism
Regional
metamorphism
Depth, km
Oceanic
crust 35
Continental crust
Oceanic
lithosphere 75
Continental mantle lithosphere
Asthenosphere
Water
Seafloor
metamorphism

24. Textures to distinguish metamorphic rocks