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Metamorphism and Metamorphic Rocks

Metamorphism and Metamorphic Rocks. A. Metamorphic rocks: Form at conditions between igneous and sedimentary rocks. Common Metamorphic Rocks. Definition Protolith : parent rock, what the rock was before it was metamorphosed. Common Metamorphic Rocks.

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Metamorphism and Metamorphic Rocks

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  1. Metamorphism and Metamorphic Rocks A. Metamorphic rocks: Form at conditions between igneous and sedimentary rocks

  2. Common Metamorphic Rocks Definition Protolith: parent rock, what the rock was before it was metamorphosed

  3. Common Metamorphic Rocks • A. Foliated: mineral grains are aligned produced by directed pressure • Slate: first product of metamorphism of shale. • Temperature: 200-350C • Relatively low temperature and pressure • 2. Phyllite: next product of shale • Temperature: 350-500C • Shiny rock with wavy layers • Low-intermediate temperature and pressure

  4. Metamorphism and Metamorphic Rocks A. Foliated—mineral grains are aligned (produced by directed pressure) 3. Schist: next product of shale Temperature: 500-650C Shiny rock with individual mica flakes now visible to the unaided eye Intermediate-high temp and pressure 4. Gneiss: next product of shale, felsic igneous rocks Temperature > 650C Minerals separate into light- and dark-colored layers High temp and pressure

  5. Metamorphism and Metamorphic Rocks A. Foliated—mineral grains are aligned (produced by directed pressure) 5. Blueshcist: oceanic basalt formed in subduction zones High pressure and low temperature

  6. Metamorphism and Metamorphic Rocks B. Nonfoliated Rocks: minerals aren’t aligned Produced with high confining Pressure (not directed pressure) Contact metamorphism Parent rock is monomineralic quartz or calcite (limestone); not elongate minerals 1. Marble: CaCO3 lack elongate minerals pure limestone

  7. Metamorphism and Metamorphic Rocks B. Nonfoliated Rocks: minerals aren’t aligned Produced at high confining pressure (not directed pressure) Contact metamorphism Parent rock is monomineralic Quartz or calcite (limestone); not elongate minerals 2. Quartzite SiO2 (quartz) Lack elongate minerals Pure quartz sandstone (most sandstones, coastal environments)

  8. Metamorphism and Metamorphic Rocks B. Nonfoliated Rocks: minerals aren’t aligned Produced with high confining pressure (not directed pressure) Contact metamorphism Parent rock is monomineralic quartz or calcite (limestone); not elongate minerals 3. Hornfels: contact metamorphism High temperature, low pressure

  9. Metamorphism and Metamorphic Rocks B. Nonfoliated Rocks: minerals aren’t aligned 3. Hornfels: contact metamorphism High temperature, low pressure

  10. Metamorphism and Metamorphic Rocks B. Nonfoliated Rocks: minerals aren’t aligned 3. Hornfels: contact metamorphism High temperature, low pressure

  11. Metamorphism and Metamorphic Rocks B. Nonfoliated Rocks: minerals aren’t aligned Produced with high confining pressure (not directed pressure) Contact metamorphism Parent rock is monomineralic quartz or calcite (limestone); not elongate minerals

  12. Metamorphism and Metamorphic Rocks

  13. Metamorphism and Plate Tectonics V. Metamorphism and Plate Tectonics Plate Movements create much of the heat, pressure and hot fluids for metamorphism Directed pressure @ convergent plate boundaries: Regional metamorphism most common Tectonic history: Blueshists: Subduction zones Hydrothermal metamorphosed basalts (not foliated: ocean basins

  14. Metamorphism and Plate Tectonics V. Metamorphism and Plate Tectonics Plate Movements create much of the heat, pressure and hot fluids for metamorphism Directed pressure - convergent plate boundaries, regional metamorphism most common Tectonic history: Blueshists: subduction zones Hydothermal metamorphosed basalts (not foliated): ocean basins

  15. Metamorphism and Plate Tectonics V. Metamorphism and Plate Tectonics Plate Movements create much of the heat, pressure and hot fluids for metamorphism Foliation  direction of ancient tectonic compression Metamorphic grade (slate, phyllite, schist, gneiss) Burial depth & amount of heat

  16. Geochronology—the study of “Earth Time” • Types of Geological Dating • Relative Dating: compares two or more groups of rocks to determine which is older and which is younger. • Non-quantitative • B. Numerical Dating: Absolute time, how long ago in years that a rock was formed or an event occurred. • Quantitative measure.

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