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Metamorphic Rocks

Metamorphic Rocks. Mr. Ahearn Earth Science 2010. What are Metamorphic Rocks?. Form at conditions between those that produce igneous and sedimentary rocks Most found under thousands of meters sed. rx. Conditions Promoting Metamorphism. Heat Pressure Circulating Fluids.

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Metamorphic Rocks

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  1. Metamorphic Rocks Mr. Ahearn Earth Science 2010

  2. What are Metamorphic Rocks? • Form at conditions between those that produce igneous and sedimentary rocks • Most found under thousands of meters sed. rx

  3. Conditions Promoting Metamorphism • Heat • Pressure • Circulating Fluids

  4. Types of Metamorphism • Regional • Contact • Other • Hydrothermal • Fault • Shock • Pyrometamorphism

  5. Regional Metamorphism • Large belts of regional metamorphism are produced when high temperature and pressure affect large regions of Earth’s crust. • can be low grade, intermediate grade, and high grade.

  6. Regional Metamorphism • Some key minerals are used to map metamorphic zones.

  7. Contact Metamorphism • contact metamorphism occurs when molten rocks, such as those in an igneous intrusion, come in contact with solid rock. (small scale) • High temperature and moderate-to-low pressure form the mineral assemblages that are characteristic of contact metamorphism.

  8. temperature decreases with distance from an intrusion, metamorphic effects also decrease with distance. limited to thin zones. Contact Metamorphism

  9. Metamorphic Textures Foliated metamorphic rocks are characterized by wavy layers and bands of minerals. • High pressure during metamorphism causes minerals with flat or needlelike crystals to form with their long axes perpendicular to the pressure.

  10. Metamorphic Textures Nonfoliated metamorphic rocks lack mineral grains with long axes in one direction. • Nonfoliated rocks are composed mainly of minerals that form with blocky crystal shapes. • Ex.  Quartzite and marble.

  11. Common Metamorphic Rocks • Foliated • Slate • Phyllite • Schist • Gneiss • Nonfoliated • Marble • Quartzite • Hornfels

  12. Amphibolite

  13. Gneiss

  14. Slate

  15. Hornsfels

  16. Phylite

  17. Marble

  18. Quartzite

  19. Schist

  20. Metamorphic Facies and Plate Tectonics • Metamorphic Facies – assemblages of different minerals that are commonly found together • Indicate specific temp & pressure conditions • Indicators of ancient subduction zones • Low temp/ high pressure • High temp/ high pressure • High temp/ low pressure

  21. Metamorphic Rock Uses • Strength and Stability • Building materials • Valued highly for appearance • Sculptors- marble, serpentinite • Talc- powder, flame resistant asbestos • Garnet- abrasive • Minerals associated with meta rx • Zinc, lead, copper, iron, gold

  22. The End

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