Term
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Definition
| Change in mineral assemblage and texture that result from subjecting a rock to conditions such as pressures, temperatures, and chemical environments different from those under which the rock originally formed |
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Term
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Definition
| A change in form that typically occurrs in sedimentary rocks, restricted to processes that occur at <200ºC |
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Term
| Where does the upper limit of metamorphism occur? |
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Definition
| Occurs at the pressure and temperature where melting of the rock in question begins. Once melting begins, the process changes to an igneous process rather than a metamorphic one. |
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Definition
| Metamorphism in which the metamorphic grade increases (as temperature and/or pressure increases) |
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Definition
| General term for describing the relative temperature and pressure conditions under which metamorphic rocks form |
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Definition
| The pressure and temperature environment in which metamorphism occurred, indicated by the observed mineral assemblages. |
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Term
| High P/T metamorphic facies series |
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Definition
characteristic of subduction zones:
(From lowest to highest)
Zeolite->Prehnite-Pumpellyite->Blueschist->Eclogite |
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Term
| Intermediate P/T metamorphic facies series |
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Definition
characteristic of continental collisions:
Zeolite->Greenschist->Amphibolite->Granulite |
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Term
| Low P/T metamorphic facies series |
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Definition
characteristic of island arcs and ocean ridge metamorphism
Zeolite->Hornfels->Sanidinite |
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Term
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Definition
| stable and very cold, with 'normal' thermal gradients ~20K/km |
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Definition
| sites where heat is advected to shallow levels, producing low P/T metamorphism |
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Term
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Definition
| Crustal extension via normal faulting leads to advection of heat to shallow levels, followed by cooling to a normal thermal gradient |
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Term
| Oceanic extension -- mid ocean ridges |
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Definition
| convection carries heat to very shallow levels, where 7-km thick oceanic crust forms; hydrothermal circulation produces low P/T metamorphism |
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Term
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Definition
| Rapid subduction advects cold material into the mantle, producing high P/T metamorphism |
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Term
| Continent-continent collisions |
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Definition
| Rapid crustal thickening produces high temperatures at moderate pressures, followed by cooling |
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Term
| Most common index mineral in greenschist facies |
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Definition
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Term
| Most common index minerals in Amphibolite facies |
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Definition
| Garnet, Staurolite, Kyanite |
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Term
| Most common index minerals in Granulite facies |
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Definition
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Term
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Definition
| a plane of constant metamorphic grade in the field; separates metamorphic zones of different metamorphic index minerals |
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Term
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Definition
Dynamic Metamorphism
Thermal Metamorphism
Dyanmo-thermal metamorphism |
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Term
| Classification of Metamorphism based on setting |
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Definition
Contact metamorphism
Regional metamorphism
Hydrothermal metamorphism
Burial metamorphism
Impact/Shock metamorphism
(C.ool R.unnings H.as B.ig S.ales) |
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Term
| What determines the size and shape of the aureole? |
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Definition
nature of the pluton: size, shape, orientation, temperature, composition
nature of the country rocks: composition, depth and met. grade prior to intrusion, permeability |
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Term
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Definition
| fine-grained rock with no foliation produced by High-T low-P metamorphism |
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Term
| Three principal types of Regional Metamorphism |
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Definition
Orogenic metamorphism
Burial metamorphism
Ocean-floor metamorphism
(O.ld B.rothas O.n-da-F.loor) |
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Term
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Definition
associated with convergient plate boundaries
Dynamo-thermal: one or more episodes of orogeny with combined elevated geothermal gradients and deformation(deviatoric stress)
Produces foliated rocks |
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Term
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Definition
Restricted to areas that have not experienced signficant deformation or orogeny (largely undisturbed sedimentary piles away from active plate margins)
i.e. Gulf of Mexico, Bengal Fan
mild deformation, no igneous intrusions; fine-grained high-temperature phases. Metamorphic effects due to increased T and P due to burial |
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Term
| Hydrothermal Metamorphism |
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Definition
| Rocks that are altered at High-T and moderate P by hydrothermal fluids. Common in basaltic rocks that generally lack hydrous minerals. |
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Term
| Shock Metamorphism (aka Impact metamorphism) |
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Definition
Occurs due to ultrahigh pressures formed at impact between meteorite/comet/large volcanic explosion impacted rocks. Ultrahigh pressures produce minerals that are only stable at very high P (i.e. coesite, stishovite)
Can produce textures like lamellae in mineral grains, shatter cones in impacted rock |
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Term
| Metamorphic Agents and Changes |
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Definition
Lithostatic pressure=uniform stress (hydrostatic: all three stress axes equal)
Deviatoric Stress=pressure unequal in different directions |
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Term
| Stress axes and how they relate to foliation/lineation |
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Definition
o1>o2=o3-->foliation, no lineation
o1=o2>o3-->lineation, no foliation
o1>o2>o3-->lineation and foliation |
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