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Rocks The Geologic Dictionary

Rocks The Geologic Dictionary. Metamorphic Rocks Rocks Under Stress

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Rocks

The Geologic Dictionary

Metamorphic Rocks

Rocks Under Stress

Metamorphism

• Recrystalization• Solid-State Chemical

Reactions• No Melting

• Parent Rock Composition

• Temperature• Pressure• Fluids

Factors that affect Metamorphism

• Parent Rock Composition

• Temperature• Pressure• Fluids

Factors that affect Metamorphism

• Parent Rock Composition

• Temperature• Pressure• Fluids

Factors that affect Metamorphism

Lithostaticpressure

DirectionalPressure

Directed Pressure Results in:

Foliation

Foliation Under a Microscope

Metamorphic Grade

• Parent Rock Composition

• Temperature• Pressure• Fluids

Factors that affect Metamorphism

Metamorphic Rocks - Identification

Metamorphic Textures(All Crystalline)

Foliated

Nonfoliated

Foliation

Composition - Index Minerals

Composition - Index Minerals

Mineral Composition - Geothermometers

Rock Forms:500-550°C

Staurolite - Forms 500-750°C

Garnet - Forms 450-700°C

Muscovite - Forms 300-550°C

Foliated Metamorphic Rocks

Parent Rock - Shale

Slate (Low Grade)

Schist (Medium Grade)

Foliated Rocks (cont.)

Felsic Parent Rock

Gneiss (High Grade)

Migmatite (Very High Grade)

NonFoliated Rocks

Parent RockLimestone

Marble(Low to High Grade)

Nonfoliated Rocks (cont.)

Quartzite

Metacoglomerate

Parent Rocks

Sandstone

Conglomerate

Metamorphic Rocks - Interpretation

Metamorphic Environments=

Metamorphic Facies

Metamorphic Rock “Translations”

• Chemical Composition

• Mineral Composition

• Foliation

• Parent Rock (Protolith)

• T & P of Formation(Depth / Facies)

• T & P of Formation (Depth / Facies)