GLGY 209 Chapter Notes - Chapter 7: Metasomatism, Hornfels, Metamorphism
8 Apr 2016
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Document Summary
Metamorphic rocks form when the crust is exposed to rising pressure and temperature condiions. Pre-exising rock that is changes due to a new assemblage of minerals. Metamorphic changes occur slowly in the solid state. Metamorphism changes mineralogy, texture, and oten imparts a foliaion upon the new rock. -> foliaion is a planar fabric that cuts through the rock. This process requires small amounts of water: plasic deformaion: happens when a rock is squeezed or sheared at elevated temperatures. The agents of metamorphism are heat (t), pressure (p), compression and shear, and hydrothermal (hot water) luids. Although they oten co-occur, not all agents are needed to alter a rock mass. Temperature: metamorphism occurs between 250 degrees celsius and 850 degrees celsius and the depth to this temperature varies with tectonic seing. Sources of heat: the geothermal gradient, magmaic intrusions, and tectonic compression.
