1. Metamorphic rocks

2. Today Updates: Midterm Lecture outline: Types of metamorphism
Prograde and retrograde

3. Types of Metamorphism Different approaches to classification
1. Based on pressure/stress and temperature:
Dynamic Metamorphism: deviatoric stress
Thermal Metamorphism: increase in T
Dynamo-thermal Metamorphism: P+T change

4. Types of Metamorphism 2. Based on setting Contact Metamorphism
Regional Metamorphism
Hydrothermal Metamorphism
Fault-Zone Metamorphism
Impact or Shock Metamorphism

5. Contact Metamorphism

6. Contact Metamorphism 2
The size and shape of an aureole is controlled by:
Pluton:
Size
Shape
Orientation
Temperature
Composition
Country rocks:
Composition
Depth and metamorphic grade prior to intrusion
Permeability

7. Contact -- rock types

8. Contact -- rock types 2

9. Regional Metamorphism

10. Regional/Orogenic Metamorphism

11. Regional/Orogenic Metamorphism 2

12. Regional/Orogenic Metamorphism 3

13. Regional/Orogenic Metamorphism 4

14. Regional: burial metamorphism

15. Hydrothermal Metamorphism
Water
Serpentinite
Basalt

16. Fault zone and impact

17. Progressive Nature of Metamorphism
Prograde
Retrograde

18. Prograde Metamorphism
Normally progress through series of mineral assemblages, for example:
epidote, chlorite, andalusite, muscovite, quartz, k-spar, and albite
sillimanite, plagioclase, cordierite, muscovite, quartz and k-spar
sillimanite, plagioclase, cordierite, quartz, and k-spar

19. Prograde Metamorphism
Retrograde

20. Retrograde Metamorphism
Prograde
Retrograde

21. Common Prograde Sequence
Index minerals make zones:
Chlorite zone. Pelitic rocks are slates or phyllites and typically contain chlorite, muscovite, quartz and albite
Biotite zone. Slates give way to phyllites and schists, with biotite, chlorite, muscovite, quartz, and albite
Garnet zone. Schists with conspicuous red almandine garnet, usually with biotite, chlorite, muscovite, quartz, and albite or oligoclase
Staurolite zone. Schists with staurolite, biotite, muscovite, quartz, garnet, and plagioclase. Some chlorite may persist
Kyanite zone. Schists with kyanite, biotite, muscovite, quartz, plagioclase, and usually garnet and staurolite
Sillimanite zone. Schists and gneisses with sillimanite, biotite, muscovite, quartz, plagioclase, garnet, and perhaps staurolite. Some kyanite may also be present (although kyanite and sillimanite are both polymorphs of Al2SiO5)

22. Sequence of indicator minerals
Sillimanite
Kyanite
Staurolite
Garnet
Biotite
Chlorite