Term
| How do metamorphic rocks form? What do metamorphic rocks form? Where do they form? |
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Definition
| Through solid state change of a pre-exisiting rock, forms new mineral assemblages and/or new textures. Form in Earths crust 10-30km |
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Term
| Metamorphic rocks are composed of what material that have recrystallized? |
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Definition
| sedimentary, igneous or metamorphic |
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Term
| What are the five processes of metamorphic rock formation, which are sometimes occur alone or together? |
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Definition
| recyrstallization, phase change, metamorphic reaction or neocrystallization, pressure solution, plastic deformation |
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Term
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Definition
| the original rock from which a metamorphic rock formed from |
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Term
| What are the causes of the formation of metamorphic rocks? 4) |
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Definition
| temperature increases, confining pressure, directed pressure, hydrothermal fluids, |
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Term
| What are hydrothermal fluids? |
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Definition
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Term
| What is the range of temperature from which metamorphic rocks derive from? |
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Definition
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Term
| metamorphism can be caused by directed pressure which results in differential stress. Define differential stress |
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Definition
| stronger or weaker forces in different directions. think of stepping on a pyramid of cards. |
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Term
| How does granite form into the metamorphic rock Gneiss? |
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Definition
| through differential stress caused by directed pressure |
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Term
| Metamorphism can be caused through hydrothermal fluids. What does this cause on the protolith rock? |
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Definition
| metamorphic reactions that change the chemistry of the rock and veins. |
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Term
| Minerals in protolith are unstable in their new environment after experiencing causes of metamorphism thus resulting in what? |
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Definition
| formation of new minerals. t and p dependent which leads to metamorphic condtions such as geothermometers and geobarometers |
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Term
| What does recrystallization do to metamorphic rocks? give an example |
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Definition
| changes shape and size of grain, not identity of mineral. ex. Protolith-sandstone, has smaller qz. metamorphic rock Quartzite has larger qz |
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Term
| What is neocrystallization |
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Definition
| the growth of new minerals that were not in the protolith. |
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Term
| Describe phase change and give an example. |
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Definition
| The transformation of a mineral that keeps the same composition but a different crystal structure. ex. Quartz to calcite. both are SiOsubscript2 |
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Term
| Describe pressure solution |
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Definition
| relatively low directed pressure and temperature and water. Mineral grains dissolve where their surfaces are pressed against other grains, producting ions that migrate through the water to precipitate elsewhere |
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Term
| descibe plastic deformation |
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Definition
| happens when a rock is squeezed at high temp and pressures. Minerals are squeezed or stretched, comp does not change |
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Term
| Metamorphic rocks can be broken down into two classes. the First class is foliation. Describe foliation |
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Definition
| the parallel surfaces or layers that can occur in a metamorphic rock, gives rock a striped appearance, can give them the ability to split into thin sheeets. |
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Term
| What causes a metamorphic rock to foliate? |
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Definition
| it contains inequant mineral crystals that are aligned parallet to one another or because the rock has alternating dark colored and light colored layers |
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Term
| How can foliated metamorphic rocks be distinguished? |
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Definition
| by their composition, grain size and the nature of their foliation |
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Term
Direct pressure on a metamorphic rock results in what class of metamorphic rocks? this creates what?
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Definition
| foliation, moutain regions |
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Term
| The finest grained foliated metamorphic rock formes by metamorphism of shale under low pressures and temps. Which rock is it? |
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Definition
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Term
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Definition
| rock splits easily along flat and parallel planes, which make it excellent for roofing shingles. Alignment of microscopic slaty minerals |
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Term
| Name the fine grained metamorphic rock with a foliation caused by the prefered orientation of very fine grained white mica |
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Definition
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Term
| under the metamorphic conditions that produce slate or phyllite, a protolith of conglomerate becomes what type of metamorphic rock? |
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Definition
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Term
| Which med rock is a medium to course grianed that possesses a type of foliation called schistophity (large mica flakes) and lso grows as visible platy or needle shaped minerals parallet to a plane? |
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Definition
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Term
| Which med rock is a compositionally layered metamorphic rock composed of alternating dark and light colored layers? |
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Definition
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Term
| When a rock forms from the melting of gneiss which produces felsic magma, still solid, mafic rock, then if the melt freezes again before flowing out of the source area, a mixture of ig and metamorphic rock forms? What is this mixture called? |
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Definition
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Term
| What are the types of foliated metamorphic rocks in order from least to highest metamorphic grade? |
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Definition
| slate,phyllite/schist, gneiss |
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Term
| describe what type of minerals nonfoliated metamorphic rocks contain |
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Definition
| minerals that recystallized or grew during metamorphism, without foliation. |
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Term
| What causes the lack of foliation in nonfoliated meta rocks? |
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Definition
| metamorphism occurred in the absence of compression/shear or tha most of the new crystals can only grown in an equant form |
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Term
| Which rock is a fine grained metamorphic rock that contains a variety of metamorphic minerals that is formed from high pressures and temps and is a contact meta rock. |
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Definition
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Term
| which meta rock forms by the metamorphism of pure quartz sandstone? give an example of the metamorphic rock it creates. |
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Definition
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Term
| The metamorphism of limestone creates what type of meta rock? |
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Definition
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Term
| Metamorphic rocks that form at low temperatures (250-400) are ____ grade rocks. metamorphic rocks that form at high temperature (over 600) are ____ grade rocks. _____ grade rocks form in between the two. |
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Definition
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Term
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Definition
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Term
| Name the four nonfoliated metamorphic rocks. |
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Definition
| Marble, Quartzite, hornfels, anthracite |
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Term
| What is metamorphic grade? give an example |
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Definition
| a wa to indicate the intensity of metamorphism, the amount or detree of metamorphic change. ex. rocks carried to a great depth beneath a mountain range undergo more intense metamorphism than do rocks closer to the surface. |
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Term
| Define metamorphic aureole/contact aureole |
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Definition
| the sistince belt of metamorphic rock that forms around the igneous intrusion |
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Term
| the local metamorphism caused by igneous intrustion can be called ________ _______ -to emphasize that it develops in response to heat w/o a change in pressure & w/o differential stress or ________ ________ -to emphasize that it develps adjacent to the contact of an intrusion with its wall rock |
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Definition
thermal metamorphism, contact metamorphism
narrow zone of contact 1-100m |
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Term
| Because thermal/contact metamorphism takes place w/o application of compression, aureoles contain what type of nonfoliated metamorphic rock? |
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Definition
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Term
| What is dynathermal metamorphism? Why is it also called regional metamorphism? |
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Definition
| metamorphism that involves not only heat, but compression and shearing. Because this metamorphism affects a lare region |
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Term
| List a few facts involved with dynamothermal/regional metamorphism. |
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Definition
| affects large areas under mountains, greater than 5km deep, 300-800degrees, occurs at convergent boundaries where one plate subducts |
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Term
| When encountering regional metamorphism, the protolith faces 3 changes. describe the three changes |
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Definition
| it heats up because of geothermal gradient/igneous activity, then it endures > Press because of the weight of overburden, lastly it undergoes compression/shearing |
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Term
| Describe burial metamorphism |
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Definition
Metamorphism occurs due to the very deep burial, -temp and press is very high, -occurs in sedimentary basins, -forms lowgrade nonfoliated metamorphic rocks, can not found oil/gas below this point
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Term
| describe dynamic metamorphism and the rock it results in. |
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Definition
occurs as a consequence of shearing alone under metamorphic conditions, takes place at anywhere that fualting occurs at depth in the crust
and results in mylonite-a rock with a foliation that parallets the fault, are very fined grained, can be found at all plate boundaries, rifts and collision zones |
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Term
| describe hydrothermal metamorphism |
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Definition
| occur at mid ocean ridges from cold water sleeping through cracks down into oceanic crust in which it is heated up and transformed into thermal fluid. Fluid then rised through crust, near ridge, thus causing hydrothermal metamorphism of ocean-floor basalt. Fluid eventually escapes through vents (black smokers) back into sea |
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Term
| Describe shock metamorphism. |
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Definition
| changes in rock due to the passage of a shock wave from large meteroties slammed into Earth, heat aand compression (shockwave) travels into earth, causes quartz in rocks below to undergo a phase change and become a compacted mineral called coesite |
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Term
| Where today can you find precambrian metamorphic rocks? (2) |
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Definition
| the Gunnison river which carved a deep canyon into the Precambrian basin rock in colorado and the eastern Canadian Shield |
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Term
| When were Precambrian rocks metamorphosed and what did this originally lead to? |
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Definition
| the succession of precambrian mountain-building, led to original growth of continents |
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Term
| What are the presence of certain minerals in a rock that indicate the approximate metamorphic grade of the rock referred as in metamorphic grading/intensity? |
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Definition
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Term
| Describe metamorphic facies. |
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Definition
| based on index mineral assembledges, named after typical meda rocks that form under certain conditions |
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Term
Metamorphic grade increases as pressure, depth and temperature increase.
Name, in order the two low, indermediate and high grade metamorphic rocks. |
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Definition
Low-slate, phyllite
Intermediate, Blue schist, schist
High-Gneiss, migmatite |
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