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Ch08_Outline - Chapter 8 Metamorphism and Metamorphic Rocks...

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1 Chapter 8 Metamorphism and Metamorphic Rocks Metamorphism The transition of one rock into another by temperatures and/or pressures unlike those in which it formed Metamorphic rocks are produced from Igneous rocks Sedimentary rocks Other metamorphic rocks Metamorphism Metamorphism progresses incrementally from low-grade to high-grade During metamorphism the rock must remain essentially solid Metamorphic settings Contact or thermal metamorphism – driven by a rise in temperature within the host rock
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2 Metamorphism Metamorphic settings Hydrothermal metamorphism – chemical alterations from hot, ion-rich water Regional metamorphism Occurs during mountain building Produces the greatest volume of metamorphic rock Rocks usually display zones of contact and/or hydrothermal metamorphism Agents of metamorphism Heat Most important agent Recrystallization results in new, stable minerals Two sources of heat Contact metamorphism – heat from magma An increase in temperature with depth due to the geothermal gradient Agents of metamorphism Pressure and differential stress Increases with depth Confining pressure applies forces equally in all directions Rocks may also be subjected to differential stress which is unequal in different directions
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