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

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Presentation on theme: "Metamorphism and Metamorphic Rocks A. Metamorphic rocks: Form at conditions between igneous and sedimentary rocks."— Presentation transcript:

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

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

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4 A. Foliated: mineral grains are aligned produced by directed pressure 1.Slate: first product of metamorphism of shale. Temperature:  C Relatively low temperature and pressure 2. Phyllite: next product of shale Temperature:  C Shiny rock with wavy layers Low-intermediate temperature and pressure Common Metamorphic Rocks

5 A. Foliated—mineral grains are aligned (produced by directed pressure) 3. Schist: next product of shale Temperature:  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 Metamorphism and Metamorphic Rocks

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

8 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: CaCO 3 lack elongate minerals pure limestone Metamorphism and Metamorphic Rocks

9 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 SiO 2 (quartz) Lack elongate minerals Pure quartz sandstone (most sandstones, coastal environments) Metamorphism and Metamorphic Rocks

10 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 Metamorphism and Metamorphic Rocks

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

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

13 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 Metamorphism and Metamorphic Rocks

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

16 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 Metamorphism and Plate Tectonics

17 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 Metamorphism and Plate Tectonics

18 I.Types of Geological Dating A. 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. Geochronology—the study of “Earth Time”


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