1. Chapter 7 Metamorphism and Metamorphic Rocks
PowerPoint Presentation
Stan Hatfield . Southwestern Illinois College
Ken Pinzke . Southwestern Illinois College
Charles Henderson . University of Calgary
Tark Hamilton. Camosun College
Copyright (c) 2005 Pearson Education Canada, Inc.

2. Metamorphosed Olympic Spirit Haircut

3. Folded Proterozoic Gneisses: (~1.1 Ga) Barrie, Ontario

4. Metamorphism
The solid state recrystallization of one rock into another by a change in conditions unlike those in which it originally formed.
Changing conditions include: Temperature, Pressure, Stress and Chemical Composition including fluids like H20 & CO2
Metamorphic rocks are produced from
Igneous rocks
Sedimentary rocks
Other metamorphic rocks

6. Paragneiss S. Greenland
Gneisses are coarsely crystalline
They have separate bands of mafic and felsic minerals
They are formed by regional “dynamo-thermal” metamorphism under collisional orogens

7. Agents of Metamorphism: Hydrostatic Pressure Differential Stress

8. Agents of Metamorphism
Shear flattening
or rotation
Confining versus directed pressure.
Development of preferred orientations.

9. Stretched Pebble Conglomerate

10. Grade of Metamorphism & T°C Gradient

11. Minerals Formed in Metamorphism
Micas: Chlorite, Chloritoid, Talc
Amphiboles: Tremolite, Actinolite, Glaucophane, Riebeckite
Pyroxenes: Jadeite, Rhodonite
Garnet: Almandine, Grossular, Spessartite
Aluminosilicates: Andalusite, Kyanite, Sillimanite
Others: Analcite, Cordierite, Corundum, Staurolite, Zeolites
Al-Geobarometers, Fe-Mg Geothermometers

12. Index Minerals & Grade for Pelitic Rocks

13. Types of Metamorphism vs T°C Gradient

14. Burial
Metamorphism
Alters Volcanics
Zeolite Facies:
Zeolites, Chlorite,
Albite, Calcite

15. Contact
Metamorphism
Bakes
Sediments
Cut by intrusion
Or overlying
Skarn Deposits:
Cu/Fe, W

16. Metamorphic Environments & Rocks
Contact Metamorphism
Clay + heat = hornfels (nonfoliated rock with mica and amphibole)
Sometimes large metamorphic minerals impart a spotted appearance = porphyroblastic
Quartzite and Marble often (not always) form by contact metamorphism from sandstone and limestone respectively
Hornfels is named for the highest Temperature metamorphic mineral it contains : Chlorite, Cordierite, Pyroxene…

17. Contact
Metamorphism
Cordierite
Porphyroblasts In
Shale
Baked to
Hornfels

18. Contact (Thermal) Metamorphism: Shallow in Crust, dT>dP, Baking near Intrusions

20. High Grade Regional
Metamorphism
Convergent Margins
Orogenic Belts:
Himalayas, Grenville,
Appalachians

21. Progressive Regional Metamorphism of Pelites

22. Development of Foliation through Shear

23. Dynamic Metamorphism Slaty Cleavage Developed By shear Leads to new
Foliation
Directions

24. Prograde Metamorphism of Basalt With Normal Geothermal Gradients
Low Medium High

25. Upper Limit of Regional Metamorphism
Migmatites:
Partial Melting
Of Low T°C
Felsic Minerals
Produces
Granitic Melt
&
Residual
Refractory
Mafic Minerals

26. Special Low dt/dP Subduction Zone Metamorphism of Basalt & Gabbro
Glaucophane Na-Fe Amphibole Omphacite & Jadeite > 100 km

27. Facies for Pelitic & Basaltic Rocks

28. Metamorphic Facies & Tectonic Settings

29. Dynamic Metamorphism: Strain >>T,P
Breccia
Mylonite
Shear ~1 Earthquake/Shallow Faults Many Quakes/Deep Faults

30. Geographic Locations of Metamorphics Ancient Continental Shields
Convergent
Margins
Ancient Continental Shields

31. Ancient Continental Shields:
Acasta Gneiss
4.03 Ga
Canadian Shield
Slave Province
NWT

32. Impact Metamorphism 49,000 Years Ago 1.186 Km across

33. Ni, Cu, PGE Discovered 1883 Construction Of CPR
Proterozoic Sudbury Impact Basin (1.85 Ga)
Cuts Archean Gneisses (2.65 Ga)
Ni, Cu, PGE
Discovered
1883
Construction
Of CPR
Grenville Orogeny is called the Penokean Orogeny ~ 1.16 Ga
Sudbury Impact Basin 1.85 Ga, Deformed in Grenville