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18 Cards in this Set
- Front
- Back
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Metamorphic rocks
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-“of changed form.” Rocks changed from one form to another by intense heat, intense pressure, or the action of watery hot fluids.
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Parent rock
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the rock type that was metamorphosed. Parent rocks can be any of the tree main rock types: igneous rock, sedimentary rock, or even metamorphic.
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Contact metamorphism
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- occurred in narrow zones next to the contact b/w parent rock and intrusive magma and along fractures in the parent rock that were intruded by hydrothermal fluids
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Regional metamorphism
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occurred over a larger region, throughout the mountain belt, and was accompanied by folding and shearing of rock layers.
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Recrystallization
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process whereby small crystals of one mineral will slowly convert to fewer, larger crystals of the same mineral, without melting of the rock.
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Neomorphism
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one way that mineralogical composition actually changes during metamorphism. Minerals not only recrystallize buy also form different minerals from the same chemical elements.
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Metasomatism
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chemical s are added or lost.
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Foliations
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layering and parallel alignment of platy mineral crystals, such as micas.
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slaty rock cleavage
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very flat foliation developed along flat, parallel, closely spaced shear planes in tightly folded clay- or mica- rich rocks. (flat surface of a blackboard or sheet of roofing)
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• Phyllite texture
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a wavy and wrinkled foliation of fine- grained platy minerals that gives the rock a satiny or metallic luster. The texture is normally developed oblique or perpendicular to a weak slaty cleavage and it is a product of intermediate- grade metamorphism.
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• Schistosity
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scaly glittery layering of visible (medium to coarse grained) platy minerals (mainly micas and chlorite) and linear alignement of long prismatic crystals (tourmaline, horblende, kyantie).
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• Gneissic banding
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alternating layers or lenses of light and dark medium – to coarse- grained minerals. Ferromagnesian minerals usually form the dark bands. Quartz or feldspars usually form the light bands.
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• Crystalline
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medium to coarse grained aggregate of intergrown, usually equal sized, visible crystals. Marble (equigranular crystalline texture).
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• Microcrystalline
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fine- grained aggregate of intergrown microscopic crystals. Hornfels is a nonfoliated metamorphic rock.
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• Sandy
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) medium to coarse grained aggregate of fused, sand- sized grains that resembles sandstone. Quartzite
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• Glassy
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homogenous texture with no visible grains or other structures and breaks along glossy surfaces. Anthracite coal
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Stretched or sheared grain
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deformed pebbles, fossils, or mineral crystals that have been stretched out, shortened, or sheared.
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Porphyroblastic
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arrangement of large crystals set in a finer- grained groundmass. It is analogous to porphyritic texture in igneous rocks.
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