1. Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador Earth Systems 3209 Unit: 3 Earth’s Materials Reference: Chapters 2, 3, 6, 7; Appendix A & B

2. Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador Metamorphic Environment - Regional Unit 3: Topic 5.3 Focus on...  describing the environments (location) where regional metamorphism occurs.

3. Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador Metamorphism  Metamorphism literally means to “change form.” These changes take thousands to millions of years to complete. During this period of change minerals within the rocks flow in solid state and can change on the atomic scale.  Metamorphism most often occurs during one of two geologic events: 1)mountain building (regional metamorphism) 2)intrusion of molten rock (contact metamorphism) Text Reference: Pages 201-205

4. Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador Regional Metamorphism  Occurs where tectonic plates collide, mainly at ocean – continent collision boundaries.  This type of environment experience compressional forces producing extensive mountain building.  The greatest volume of metamorphic rocks are formed in this way.  This type of metamorphism is caused by two main conditions: 1) extreme pressure 2) extreme heat. Mountain Environment

5. Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador Pressure  Pressure on rocks within mountain environments is mainly caused by: 1)confining pressure caused by the weight of the material above, and 2)directional stress caused by compressional forces as tectonic plates push against one another.  This pressure causes rocks to deform and flow as if they were plastic.  The minerals within the rocks recrystallize and reorganize to form metamorphic textures. Folding is a common feature found in rocks that have undergone regional metamorphism. Regional Metamorphism

6. Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador Regional Metamorphism Heat  Heat involved in regional metamorphism within mountain environments is the result of: 1) Geothermal gradient which states that temperature increases 30 degrees Celsius for each kilometer below the surface, and; 2) Intrusion of hot molten rock called magma which causes the surrounding rock to heat up as heat from magma radiates outward.

7. Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador  WHERE DOES IT OCCUR? 1)Areas of mountain building; and 2) Subduction zones.  Ocean-continent collision (convergent plate boundary) is an example of where subduction and mountain building occurs.  A compressional environment resulting in increasing pressure. As the mountains are forming, increasing burial depth results in increasing temperatures. These conditions led to the formation of metamorphic rock. (1) Regional Metamorphism

8. Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador  This is a subduction zone. The metamorphism is not occurring within the subduction zone, but within the mountain system. As you can see, as burial depth increases so does the GRADE OF METAMORPHISM. Regional Metamorphism Shale to Slate to Phyllite to Schist to Gneiss (2) Text Reference Page 204

9. Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador Example 1: In which environment does regional metamorphism occur? (A) deep marine (B) magma chamber (C) mountain belt(D) shallow marine

10. Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador Example 2: Explain the sequence from A through D that will occur in shale as it is buried deeper within the folded mountains at a continental - continental plate collision.

11. Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador Example 2: (Answer) Shale is a clastic sedimentary rock that is capable of being metamorphosed. As shale is buried deeper and deeper in Earth’s crust heat and pressure increase. Consequently, the degree of metamorphism will also increase (i.e. low grade through to high grade), producing a predictable sequence of rocks as follows: Shale is metamorphosed into slate at location A. Slate is metamorphosed into phyllite at location B. With increasing burial phyllite changes into schist at location C. Finally, at location D schist changes to form the highest grade metamorphic rock, called gneiss.

12. Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador Your Turn... Take the time and complete the following questions... (Solutions to follow) Question: Contrast the conditions necessary for a rock to change by regional metamorphism compared to that of contact metamorphism.

13. Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador Solutions... Question: Contrast the conditions necessary for rock to change by regional metamorphism compared to that of contact metamorphism. Answer: Regional metamorphism occurs in mountainous environments, where rocks are exposed to high heat from igneous intrusions and high pressure caused by compressional forces. Contact metamorphism can occur in any environment where a heat source (molten rock) causes the surrounding rock to change. Thus, regional metamorphism is caused by high heat and high pressure, whereas, contact metamorphism is caused by heat only.

14. Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador Summary... Overview of Points covered: Regional Metamorphism:  Forms in areas of high heat and pressure.  Associated with;  Mountain building  Collision boundaries (Subduction zones)  Forms high grade of metamorphic rocks.