Metamorphic Rocks
Protolith
Origin of Metamorphic Rocks
Heat
Diffusion
Pressure
Fluids
Geologic Forces
Stress – Force applied to an area
Differential stress – when the magnitude of
stress is not equal in all directions.
Normal Stress
Shear Stress
Differential Stress
Stress Induced Foliation
Preferred Mineral Orientation
Wet Rock and Hot Fluids
Metasomatism
Hydrothermal Alteration
Serpentinite
Metamorphic Environments???
Contact Metamorphism
Regional Metamorphism
Regional
Metamorphism
Burial Metamorphism
Dynamic Metamorphism
Nonfoliated
Metamorphic Texture
Foliated
Metamorphic Texture
Metamorphism of Shale
Slate
• Very Fine Grained
• Low Grade Metamorphism
Phyllite
• Larger micaceous minerals
• Low Grade Metamorphism
• Luster
Schist
• Medium to Course Grained
• High Grade Metamorphism
• Large platy minerals (micas, chlorite, talc)
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Gneiss
Foliated – light and dark bands
Course Grained – Granular
High Grade Metamorphism
Quartz, feldspar, biotite, amphibole, garnet
Migmatite
• Part igneous, part metamorphic
• Commonly have thin dikes and sills
Quartzite
• Nonfoliated
• Course Grained - Granular
• Some sedimentary features survive
• Parent rock – Quartz-rich sandstone
Marble
• Nonfoliated
• Course Grained - Granular
• Parent rock – Limestone and Dolomite
Marble
Hornfels
• Fine-grained
• Nonfoliated
• Dark colored
• Results from contact metamorphism
Mylonite
• Very fine grained
• Weakly foliated
• A product of intense shearing
Metamorphic Facies
•Garnet and Staurolite
Metamorphic Facies
•Garnet and Staurolite
•600 to 700o C
•15 km depth
•Granitic Dikes
•Deformation structures
Zoned Garnets