8._METAMORPHIC_ROCKS_white

8._METAMORPHIC_ROCKS_white - METAMORPHIC ROCKS Metaphorphic...

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METAMORPHIC ROCKS
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Metaphorphic Rocks Metamorphism refers to solid-state changes to rocks in Earth’s interior Produced by increased heat, pressure , or the action of hot, reactive fluids Old minerals, unstable under new conditions, recrystallize into stable ones
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Metaphorphic Rocks Rocks produced from pre-existing or parent rocks in this way are called metamorphic rocks Metamorphic rocks common in the old, stable cores of continents, known as cratons Mapsorama.com
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Factors Controlling Metamorphic Rock Characteristics Texture and mineral content of metamorphic rocks depend on: Parent rock composition Temperature and pressure during metamorphism Effects of tectonic forces Effects of fluids , such as water
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Factors Controlling Metamorphic Rock Characteristics Parent rock composition Usually no new material (other than water) is added to rock during metamorphism Resulting metamorphic rock will have similar composition to parent rock
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Factors Controlling Metamorphic Rock Characteristics Temperature during metamorphism Heat for metamorphism comes from Earth’s deep interior All minerals stable over finite temperature range If range exceeded, new minerals result If temperature gets high enough, melting will occur
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Factors Controlling Metamorphic Rock Characteristics Pressure during metamorphism Confining pressure applied equally in all directions Pressure proportional to depth within the Earth increases ~1 kilobar per 3.3 km
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Factors Controlling Metamorphic Rock Characteristics Tectonic forces Often lead to forces that are not equal in all directions ( differential stress ) Compressive stress causes flattening perpendicular to stress
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Differential Stress Metaconglomerate Conglomerate
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Factors Controlling Metamorphic Rock Characteristics Tectonic forces Shearing causes flattening by sliding parallel to stress Planar rock texture of aligned minerals produced by differential stress is known as foliation Foliation increases with pressure and
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Foliation Minerals grow parallel to shearing or perpendicular to compressive stress
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This note was uploaded on 03/06/2012 for the course GEO 505 taught by Professor Johnschmidt during the Spring '12 term at CUNY Graduate School of Journalism.

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8._METAMORPHIC_ROCKS_white - METAMORPHIC ROCKS Metaphorphic...

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