Earth Sciences 1022A/B Chapter Notes - Chapter 6: Metamorphic Rock, Clay Minerals, Geothermal Gradient
15 Nov 2018
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Document Summary
Formed by the recrystallization/reformation of minerals within an existing rock. Sedimentary or igneous rocks recrystallize at when the temperature or pressure is higher than the conditions where they crystallized. Factors affecting mineral makeup of the metamorphic rock: Composition of the fluid phase of the rock. The water in clay mineral structure is released and acts to promote migration of chemical components. Fluids dissolve minerals and precipite them into areas of lower stress. Although minerals of the rock change, overall chemical composition does not. Usually results in a recrystallization and/or coarsening of minerals. Temperature increase about 20o to 30o per km. Determined by the intensity of metamorphism (pressure and temperature) Use index minerals to determine metamorphic grade. Mild (only slight increases in pressure and temperature) Forms zeolites (hydration of silicates) and chlorites. Occurs at a depth of 8 km and around 200oc. Rocks are subjected to confining pressure (equal in all directions) Gets denser (but does not get distorted or deformed)
