1. METAMORPHIC ROCKS

2. METAMORPHIC ROCKS What is Metamorphism? What Drives Metamorphism?
Metamorphic Textures
Common Metamorphic Rocks

3. Metamorphic Rocks
What Is Metamorphism?

4. WHAT IS METAMORPHISM? “meta” = change; “morph” = shape
PSCI 131: Metamorphic Rocks
WHAT IS METAMORPHISM?
“meta” = change; “morph” = shape
Change of one rock type into another
Heat and (usually) pressure
Parent rock
Rock that gets metamorphosed into something else
ANY rock type can be a parent rock, including a metamorphic rock

5. What Drives Metamorphism?
Metamorphic Rocks
What Drives Metamorphism?

6. Three Metamorphic Agents
PSCI 131: Metamorphic Rocks: What Drives Metamorphism?
Three Metamorphic Agents
Heat: most critical
Pressure
Chemically active fluids

7. Heat A form of energy Vibration of atoms and molecules
PSCI 131: Metamorphic Rocks: What Drives Metamorphism?
Heat
A form of energy
Vibration of atoms and molecules
Hotter = faster vibration

8. Role of Heat in Metamorphism
PSCI 131: Metamorphic Rocks: What Drives Metamorphism?
Role of Heat in Metamorphism
Provides energy for chemical reactions
Weakens atomic bonds in mineral crystals

9. Pressure Confining pressure Differential stress
PSCI 131: Metamorphic Rocks: What Drives Metamorphism?
Pressure
Confining pressure
Differential stress

10. Confining Pressure Equal in all directions Deep burial
PSCI 131: Metamorphic Rocks: What Drives Metamorphism?
Confining Pressure
Equal in all directions
Deep burial

11. Differential Stress Higher pressure from sides
PSCI 131: Metamorphic Rocks: What Drives Metamorphism?
Differential Stress
Higher pressure from sides
Converging tectonic plates
Zone of intense differential stress

12. Chemically Active Fluids
PSCI 131: Metamorphic Rocks: What Drives Metamorphism?
Chemically Active Fluids
Some minerals are hydrated
E.g. gypsum CaSO4 + 2H20
Water driven out of these minerals by heat
Circulating water promotes transport of atoms

13. Metamorphic Rocks
Metamorphic Textures

14. Foliation Created by differential stress
PSCI 131: Metamorphic Rocks: Textures
Foliation
Created by differential stress
Preferred orientation of elongated minerals

15. Foliated Textures Slaty cleavage Gneissic texture Schistosity
PSCI 131: Metamorphic Rocks: Textures
Foliated Textures
Slaty cleavage
Gneissic texture
Schistosity

16. Nonfoliated Textures Interlocking grains
PSCI 131: Metamorphic Rocks: Textures
Nonfoliated Textures
Interlocking grains
Confining pressure or absence of pressure

17. Nonfoliated Textures PSCI 131: Metamorphic Rocks: Textures
Limestone metamorphoses into the nonfoliated rock marble.
Marble, made of interlocking calcite grains.

18. Common Metamorphic Rocks

19. Common Foliated Rocks Slate Phyllite Schist Gneiss
PSCI 131: Metamorphic Rocks: Common Types
Common Foliated Rocks
Slate
Phyllite
Schist
Gneiss
From: radford.edu

20. Common Nonfoliated Rocks
PSCI 131: Metamorphic Rocks: Common Types
Common Nonfoliated Rocks
Quartzite
Parent: sandstone
Marble
Parent: limestone
Anthracite
Parent: coal

21. End of Metamorphic Rocks