Metamorphic
A. Any rock that is changed by extreme forms of heat
& pressure which, results in mineral recrystallization.
1.
2.
3.
They Do Not Melt!!!!
Parent material comes from other rocks.
Usually very hard and dense showing some distorted layers
B. Metamorphics are classified by their
texture & composition.
Foliated Textures: “show distortion”
Mineral Alignment:
- The minerals are squished into flat layers
- Schistocity: Low grade metamorphic pressure
Ex. Slate, Phylite, Schist
Banding:
- Minerals are separated into different layers
- Movement of crystals without melting
- Seperated by mineral density differences
- High grade metamorphism
Ex. Gneiss
Formation of Metamorphic Rocks
Stage 1 Mineral Alignment
Pressure
x
z
z
zY x
x Y
x Y
z Y
z
x
Heat
x
-Original parent rock with minerals in
rock structure. (X,Y,Z).
z
- Rock is subject to low grade pressure
& temperatures & then the minerals are
flattened.
Stage 2 Banding
"Recrystallization"
extreme heat & pressure allows individual crystals to…
- Grow larger
- Consolidate together
- Separate according to density differences.
x
x z Y xz x
x
xz
zz z
x z x Y
Y Yx z Y
Yz
z xY z Y
Y x Y
xzxx x x x x
zz z zx xz zz z x
z z Y
YY YY Y Y
Y YY
C. Types of Metamorphic processes.
1. Contact: Occurs when molten rock (intrusion or extrusion)
comes into contact with surrounding materials.
- Intrusion will always be the younger rock
- Heat is the primary agent for metamorphism.
2. Regional: Occurs over large areas under mountain ranges.
Foliated Rocks
Usually are derived from many mineral types.
Phylite Schist
Gneiss
Increasing Depth,
Pressure & Temperature
Non-foliated Rocks
Usually are derived from one mineral type.
Quartzite
Marble