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Metamorphism

Metamorphism. Chapter 6 Pages 130-149. Causes of Metamorphism. Internal heat of the Earth Pressure Fluid composition. Role of Temperature. Larger crystals are formed in rocks during metamorphism Increased geothermal gradient such as 30 o C per km of depth

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Metamorphism

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  1. Metamorphism Chapter 6 Pages 130-149

  2. Causes of Metamorphism • Internal heat of the Earth • Pressure • Fluid composition

  3. Role of Temperature • Larger crystals are formed in rocks during metamorphism • Increased geothermal gradient such as 30o C per km of depth • Increase plate tectonic processes

  4. The role of Pressure • Two types of pressure or stress • 1. Confining pressure • 2. Directed pressure

  5. Role of Fluids • The role of fluids in metamorphic rocks can be due to: • A. Hydrothermal fluids • B. Metasomatism

  6. Types of Metamorphism • Regional metamorphism • Contact metamorphism • Seafloor metamorphism • Burial metamorphism • Shock metmorphism

  7. Regional Metamorphism • Is most common type • Found with convergent plate tectonics • Created by high temperatures and by moderate to high pressures

  8. Contact Metamorphism • Often occurs when heat from igneous intrusions metamorphoses the immediate surrounding rocks. • Can also affect blocks of magma

  9. Seafloor metamorphism • Occurs at mid ocean ridges • AKA metasomatism • Can get chemical reactions between sea water and the rocks

  10. Low grade or Burial Meta. • Caused by an increase of heat and an increase of pressure • Occurs at 6 to 10 km deep

  11. Shock metamorphism • Occurs when a meteorite hits the Earth • Formation of Tektites • Rare occurrence on Earth • Happens a lot on the Moon

  12. Classification of Foliated rocks • Based on four things: • A. The size of their crystals • B. The nature of their foliations • C. The degree to which the minerals are segregated into lighter and darker bands • D. Their Metamorphic grade

  13. Metamorphic grades • 1. Slate • 2. Phylites • 3. Schist • 4. Gneiss • 5. Migmatite

  14. Granoblastic rocks • Types of Granoblastic rocks: • 1. Hornfels • 2. Quartzites • 3. Marbles • 4. Greenstones • 5. Amphibotite

  15. Table 6.1 Classification by Texture • Page 140

  16. Table 6.2 Facies and Minerals • Page 143

  17. Plate Tectonics and Metamorphism • Plate Interiors • Divergent plates • Convergent plate Margins • Transform plate margins

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