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Note: Metamorphism
Metamorphism: Transformation of rock texture &/or mineralogy that occurs in
the solid state (i.e. no melting)
Parent rock is unstable under new conditions
Evidence that metamorphism occurs in a solid state (i.e. no melting occurs):
Contorted banding:
Types of Metamorphism
1. Contact Metamorphism
Metamorphism occurs due to heat.
Source of heat is a nearby magma chamber (pluton or diapir)
Rock next to the magma heats up and the minerals change (no melting).
These rocks are found in layers between igneous and sedimentary rocks
2. Regional Metamorphism
Accounts for majority of metamorphic rocks
Occurs due to
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Confining pressure:
Compressive Stress:
force is applied in opposite directions
Elongate or platy minerals form during re-crystallization
Results in a “foliated” texture
Source of compressive stress:
3. Hydrothermal Metamorphism
Hot water seeps between grains of rock or in rock joints
Metamorphic Rock Textures (i)
Foliation:
Types of foliation:
1.Slaty: rock splits
easily along flat,
parallel planes.
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2. Schistose: visible platy or needle-shaped minerals - can be folded and does
not split easily
3. Gneissic: during metamorphism, minerals separate into light and dark
layers.
Metamorphic rocks that you should know of:
Foliated:
Slate
Phyllite
Schist
Gneiss
Non-Foliated
Marble
Quartzite
Hornfels
Practice #1
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Practice #2
Practice #3
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