metamorphic rocks - fossilhub · 2013-10-31 · metamorphic rocks metamorphism . 31/10/2013 2...
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5. Under Pressure
Metamorphic Rocks
Metamorphism
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Metamorphism
Heat and pressure
Can affect any rock
Low-High grade
Solid state change
Hand specimens
First impressions?
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Metamorphism
Temperature >200°C
AND/OR
Pressure >300 MPa (3 kbar)
AND/OR
Chemically active fluids
Metamorphic facies
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Thermal metamorphism
Igneous intrusion bakes surrounding rocks
Thermal metamorphism
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Hornfels
Marble
Thermal metamorphism
Marble crystals
Limestone grains
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Metamorphism by pressure
Metamorphism by pressure SLATE
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Metamorphism by pressure
SLATE
SLATE
Regional metamorphism
High temps and pressures
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= High-grade metamorphism
Mechanical metamorphism
Mylonite = milled
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Chemical metamorphism
Metasomatism:
Soapstone
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Key metamorphic features
Cleavage:
Slaty cleavage
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Welsh slate
belts
Penrhyn Slate Quarry,
Bethesda, c. 1900
Foliation
Schist under the microscope
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Multiple foliation
Banding Gneiss, Stockholm
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Partial melting migmatite
Metamorphic zones
andalusite
Almandine garnet
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Metamorphic facies
Next week Folds, Faults & Plate Tectonics