Term
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Definition
| a process that leads to changes in the mineralogy, texture, and sometimes chemical composition of rocks |
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Term
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Definition
| rock from which a metamorphic rock is formed |
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Term
| when does metamorphism take place |
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Definition
| when a preexisting rock is subject to new conditions that are significantly different from those in which it initially formed |
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Term
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Definition
| heat, pressure (stress), and chemically active fluids |
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Term
| what is the most important factor in metamorphism and why |
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Definition
heat
it provides energy needed to drive the chemical reactions that result in recrystallization |
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Term
| how does heat cause change |
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Definition
it promotes recrystallization
it causes rocks to eventually reach an unstable temp. causing the atoms to rearrange themselves |
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Term
| where does heat come from |
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Definition
earths internal heat comes from energy being released by radioactive decay and thermal energy
can also be transported from the mantle through igneous intrusions |
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Term
| what is confining pressure |
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Definition
| analogous water pressure in which forces are applied equally in all directions |
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Term
| what does confining pressure cause |
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Definition
| the spaces between mineral grains to close causing a more compact rock |
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Term
| what is differential stress |
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Definition
| forces that deform rocks are unequal in different directions |
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Term
| what is the result of differential stress |
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Definition
| rocks becoming folded or flattened |
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Term
| when rocks exhibit ductile behavior they do what |
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Definition
| their mineral grains tend to flatten and elongate when subjected to differential stress |
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Term
| what does a mineral being hydrated mean and what are examples |
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Definition
it contains water
clays and micas |
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Term
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Definition
| when substantial chemical change accompanies metamorphism |
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Term
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Definition
| refers to any planar (nearly flat) arrangement of mineral grains or structures within a rock |
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Term
| what are 3 diverse types of foliation |
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Definition
1. rotation of mineral grains into a parallel orientation
2. recrystallization that produces new minerals with grains that exhibit a preferred orientation
3. change of spherically shaped grains into elongated shaped that are aligned in preferred orientation |
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Term
| what are the 3 types of foliated textures |
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Definition
rock or slaty cleavage
schistosity
gneissic |
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Term
| what is rock cleavage texture |
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Definition
| refers to closely spaced flat surfaces along which rocks split into thin slabs when broken |
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Term
| what is schistosity texture |
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Definition
when under high pressure regimes crystals begin to grow
when they are big enough to see with the naked eye this is called schistosity |
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Term
| describe gneissic texture |
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Definition
| during high grade metamorphism ion migration can result in the segregation of minerals giving the rock a banded appearance |
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Term
| what are nonfoliated rocks |
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Definition
| rocks with a nonfoliated texture |
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Term
| describe porphyroblastic texture |
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Definition
| the rock consists of unusually large grains called porphyroblasts that are surrounded by a fine-grained matrix of other minerals |
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Term
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Definition
foliated
very fine grained
composed of minute mica flakes
excellent cleavage |
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Term
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Definition
foliated
middle ground between slate and schist
platy minerals larger than slate but too small to see
composed of muscovite or chlorite |
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Term
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Definition
foliated
medium to coarse grained
contains micas, quartz and feldspar |
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Term
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Definition
medium to coarse grained
banded appearance
mainly quartz and feldspar
bad cleavage |
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Term
| what are examples of foliated rocks |
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Definition
| slate, phyllite, schist, gneiss |
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Term
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Definition
nonfoliated
coarse, crystalline
parent was limestone or dolostone
relatively soft |
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Term
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Definition
non foliated
very hard
parent - quartz sandstone |
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Term
| describe contact or thermal metamorphism |
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Definition
| occurs when rocks immediately around a molten igneous body are "baked" and therefore altered from their original state |
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Term
| what is a metamorphic aureole |
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Definition
| the area in which alteration of rocks occurs |
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Term
| what is hydrothermal radiation |
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Definition
when hot, ion rich fluids circulate through fissures and cracks in a rock
created hydrated silicates |
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Term
| what are examples of hydrated silicates |
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Definition
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Term
| what is burial metamorphism |
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Definition
confining pressure and geothermal heat drive the recrystallization of the constituent minerals
changing the texture and/or mineralogy without appreciable deformation |
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Term
| what is subduction zone metamorphism |
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Definition
| rocks and sediments being carried great depths along convergent boundaries where oceanic lithosphere is being sub ducted |
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Term
| how does subduction zone metamorphism differ from burial metamorphism |
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Definition
| differential stress plays a major role in deforming rocks |
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Term
| what is regional metamorphism |
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Definition
| metamorphic rock is produced during mtn. building when large segments of earths crust are deformed |
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Term
| when is most metamorphic rock produced |
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Definition
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Term
| describe impact metamorphism |
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Definition
| occurs when high speed projectiles called meteorites strike earths surface |
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Term
| what are the results of impact metamorphism called |
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Definition
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Term
| describe a migmatite rock |
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Definition
| when rocks are heated and have partially melted components that then resolidify into bands on the rock |
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Term
| what are metamorphic facies |
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Definition
| metamorphic rocks containing the same assemblage of minerals |
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Term
| what are some example of metamorphic facies |
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Definition
| hornfels, zeolite, granulite, blueschist |
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Term
| what role do chemically active fluids play in metamorphism |
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Definition
heat agent
material transfer
promote chemical reactions |
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Term
| where does most hydrothermal metamorphism occur |
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Definition
| along the axis of the mid-ocean ridge system |
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Term
| with what type of plate boundary is regional metamorphism associated |
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Definition
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Term
| why do the cores of earths major mtn. chains contain metamorphic rock |
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Definition
| pressure and heated volatiles force realignments in crystals when the mountains are formed |
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