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26 Cards in this Set
- Front
- Back
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Metamorphic Rocks
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Formed as a result of mineralogical and textural changes that occur as rocks are subjected to high temperatures and pressures within the earth's crust.
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How much of the earth's crust is metamorphic?
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35%
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Solid State
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a condition where the minerals do no melt. Instead, recrystallization occurs.
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Recrystallization
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both the textures and mineral compositions change when metamorphic conditions of heat and pressure are applied.
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Temperature range for metamorphism
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approx. 155 - 500ºC
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Lithostatic pressure range
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2,000 - 10,000 bars
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Lithostatic Pressure
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The weight of overlying column on a unit area (ex. 1 sq meter)
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4 geological provinces of Georgia
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1 - Piedmont
2 - Coastal Plain 3 - Valley and Ridge 4 - Blue Ridge Mtns |
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Piedmont province
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Metamorphic rocks; metamorphosed with push up of appalachain mtns ~350-250 millions ago.
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Coastal Plain province
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Younger sedimentary rock, deposited after uplift of Appalachian Mtns ~100 million years ago to the present.
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Valley and Ridge Province
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Older sedimentary rock deposited before the push up of the Appalachian Mtns. 600 - 350 million years ago.
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pressure =
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3000kg/m3 x 980 m/s2 (gravity) x height
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Metamorphic Facies
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a set of minerals that correspond to variable metamorphic "grades" of temp and pressure
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Strain makes rocks...
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Stronger
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Foliation
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a term which roughly describes some form of parallel arrangement of mineral grains.
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Interlocking
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grains in metamorphic rocks that interlock with one another as a result of pressure.
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In general, grains in metamorphic rocks line up _______ to pressure
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perpendicular
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Slate
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Characterized by slatey cleavage. "compressed shale." Slate does not tear apart.
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Schist
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Parallel arrangement of micas which are flat "platey" minerals. Texture known as "schistosity," which means something like "to shine."
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Gneiss
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Texture is known as gneissic banding. Under high grade metamorphic conditions, the mineral rearrangements result in separation of light and dark minerals, leaving the rock banded.
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Non-foliated metamorphic rocks have __________ textures.
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Interlocking
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Non-foliated metamorphic rock types
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Quartzite and Marble
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Quartzite
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Interlocking quartz crystals
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Marble
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Interlocking calcite and dolomite grains. > 50% calcite
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Contact metamorphism
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Heat is the principal agent of metamorphism - temps as high as 600ºC are responsible. Usually limited to the margins of cooling plutons.
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Regional Metamorphism
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Pressure is the principal agent of metamorphism. Occurs over large areas.
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