Metamorphic Rocks #9 Ch.6

Metamorphism

changes in the mineral chemistry and/or textures that happen in the solid state

What causes metamorphism?

temperature, pressure, and fluids

What is foliation?

layering in the metamorphic rocks

How is foliation caused?

by parallel alignment of sheet like minerals especially the micas - biotite and muscovite

What are the foliate rock types?

Slate, Phyllite, Schist, and Gneiss

What are the non foliated rock types?

Marble, Quartzite, Hornfels, Anthracite Coal

How can we determine the severity of metamorphism?

index minerals

What are index minerals?

sensitive indicators of metamorphic conditions

What are examples of index minerals?

• Garnet and muscovite

• quarts and feldspar are NOT good index minerals

What does prograde metamorphism mean?

increasing temperature and pressure

What does retrograde metamorphism mean?

decreasing temperature and pressure

At what “scales” does metamorphism occur?

Contact metamorphism and Regional metamorphism

What causes regional scale metamorphism?

Burial and plate tectonics

Why are high grade rocks found at Earth’s surface?

Decreasing temperature during uplift and cooling, so reaction rates are slowed - exponentially as temperature decreases