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54 Cards in this Set
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Common facies for contact metamorphism metabasite.
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Albite-epidote hornfels facies, Hornblende hornfels facies, Pyroxene hornfels facies, and sanidine facies
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define hornfels
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massive, undeformed rock with a granular fabric lacking any preferred orientation (lineation, foliation); characteristically has a 'spotty' appearance.
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what restriction does one have in contact metamorphism?
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Contact metamorphic facies are best defined by pelite mineral assemblages; the higher-T facies are uncommon
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Common facies for contact metamorphism pelite.
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Albite-epidote hornfels, Hornblende hornfels, Pyroxene hornfels , and sanidine
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define Albite-epidote hornfels facies in metabasite contact metamorphism and common assemblages.
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low-P equivalent of the greenschist-facies.
Assemblage: ab + ep + act + chl ± bio, qz |
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define Hornblende hornfels facies in metabasite contact metamorphism and common assemblages.
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low-P equivalent of the amphibolite-facies.
Assemblage: hbl + act + anth + plg + gt ± bio, qz |
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define Pyroxene hornfels facies in metabasite contact metamorphism and common assemblages.
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low-P equivalent of the granulite-facies.
Assemblage: cpx + opx + plg + gt ± hbl, bio, qz |
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define sanidine facies in metabasite contact metamorphism and common assemblages.
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not well defined for metabasite
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define Albite-epidote hornfels in pelite contact metamorphism and common assemblages/diagnostic minerals.
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chl diagnostic.
Assemblage: ms + bio + chl + ab + qz ± kf |
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define Hornblende hornfels in pelite contact metamorphism and common assemblages/diagnostic minerals.
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cd + ms diagnostic.
Assemblage: cd + ms + bio + plg + qz ± kf, gt, |
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define Pyroxene hornfels in pelite contact metamorphism and common assemblages/diagnostic minerals.
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cd + and + kf diagnostic.
Assemblage: cd + and + kf + plg + bio + qz ± gt |
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define Sanidinite in pelite contact metamorphism and common assemblages/diagnostic minerals.
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glass diagnostic; kf is sanidine.
Assemblage: cd + kf + plg + glass |
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define zeolite facies in metabasite in regional metamorphism.
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Zeolite-facies minerals common as fracture or vesicle fillings in massive basalt.
Calcite replaced by albite. presence of the zeolite mineral laumontite diagnostic. Secondary quartz, calcite, and fine-grained phyllosilicate (chlorite) are commonly also formed. |
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define zeolite facies in pelite in regional metamorphism.
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Only calcic bulk compositions develop zeolite.
Original clay minerals (smectite or montmorillonite) become mixed-layer (illite-smectite) clay. smectite + fsp = illite-smectite + qz |
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define Prehnite-Pumpellyite-Facies regional metamorphism in metabasite.
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Presence of prehnite [Ca2Al2Si3O10(OH)2] and pumpellyite [Ca4(Mg,Fe)(Al,Fe)5Si6O23(OH)3.2H2O] diagnostic
Quartz, albite, chlorite, and calcite are common additional secondary minerals. relic igneous textures preserved. |
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define Prehnite-Pumpellyite-Facies regional metamorphism in pelite.
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Only calcic bulk compositions develop prehnite and pumpellyite.<>
Mixed-layer clay minerals become more ordered illite (illite crystallinity increases). illite-smectite + qz ± chl = illite + qz ± chl must have hydrocirculutation |
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define Greenschist-Facies regional metamorphism in metabasite.
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Presence of actinolite diagnostic, but at higher P-T actinolite replaced by a blue-green hornblende; plagioclase is sodic
act + ep + ab + chl + qz at lower T hbl ± act + ep + ab + chl ± gt at higher T |
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define Greenschist-Facies regional metamorphism in pelite.
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Chlorite, biotite, garnet Barrovian zones.
Chlorite diagnositic. Assemblage: chl + ms + ab + qz chlorite zone Assemblage: bio + chl + ms + ab + qz biotite zone Assemblage: gt + chl + bio + ms + ab + qz garnet zone |
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define amphibolite facies regional metamorphism in metabasite
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Absence of actinolite and plagioclase is more calcic than in the greenschist-facies.
Assemblage: hbl + plg (³An17) ± ep ± gt ± qz chl + Al-ep + qz = hbl + an + H2O ab + act = hbl + qz act + chl + qz + Al-ep = hbl + H2O |
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define amphibolite facies regional metamorphism in pelite
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Staurolite, kyanite, sillimanite Barrovian zones.
Assemblage: st + bio + musc + qz + ab + gt ± chl staurolite zone ctd + qz = st + gt + H2O chl + ms + gt = st + bio + qz + H2O chl + ms = st + bio + qz + H2O Assemblage: ky + bio + ms + qz + ab + gt ± st kyanite zone chl + ms + qz = ky + bio + H2O st + chl + ms = ky + bio + qz + H2O st + ms + qz = ky + bio + H2O Assemblage: sil + bio + ms + qz + ab + gt ± st, ky sillimanite zone ky = sil st + ms + qz = sil + bio + H2O |
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define blueshist facies in regional metamorphism of metabasite
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High P
Glaucophane + lawsonite (CaAl2Si2O7(OH)2.H2O) is diagnostic Assemblage: gl + law ± jd, chl, qz, ms, ag |
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define blueshist facies in regional metamorphism of pelite
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High P
Gl + law again diagnostic, but presence (especially of law) depends on bulk composition. No biotite. gl + phengite + chl + qz ± law, jd, ag |
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define Eclogite-Facies regional Metamorphism in metabasite
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Mineralogy is predominantly pyralspite garnet plus the sodic pyroxene omphacite.
Assemblage: gt + om ± qz ± rt ± ky No plag |
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define Eclogite-Facies regional Metamorphism in pelite
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Metamorphism of pelite at very high-P produces unusual whiteschist of mostly kyanite and talc [Mg6Si8O20(OH)4].
Assemblage: tc + ky + qz ± gt ± musc |
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define Amphibolite
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a metamorphic rock (typically a metabasite) predominantly comprising
hornblende and plagioclase; a mineral assemblage characteristic of the amphibolite-facies. |
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define Blueschist
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a metabasite containing abundant sodic amphibole; a mineral assemblage
characteristic of the blueschist-facies. |
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define Corona
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mineral surrounded by a rim or mantle of another mineral(s); a reaction rim.
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define Calc-silicate
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a metamorphic rock derived from a marly sedimentary protolith
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define Charnockite
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a K-feldspar and hypersthene bearing granulite.
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define Eclogite
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a metabasite composed predominantly of garnet and omphacite; a mineral
assemblage characteristic of the eclogite-facies |
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define Foliation
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alignment of platy mineral grains perpendicular to the direction of maximum applied
stress. |
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define Gneiss
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a coarse grained, foliated rock typically showing segregation of feldspar- and quartzrich
layers and mafic- and mica-rich layers. |
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define Granulite
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a metamorphic rock characterized by equidimensional, polygonal grains of all
minerals which are typically feldspar, pyroxene, amphibole; a mineral assemblage characteristic of the granulite-facies. |
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define Greenschist
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a metabasite composed predominantly of chlorite, epidote, and actinolite; a
mineral assemblage characteristic of the greenschist-facies. |
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define hornfels
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a contact metamorphic rock comprising a random fabric of interlocking grains.
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define Idioblast
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a porphyroblast with well developed crystal faces (= euhedral).
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define Lineation
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- alignment, parallel to the direction of stretching, of elongate grains.
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define Marble
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a metamorphic rock derived from a carbonate-rich sedimentary protolith.
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define Metabasite
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a metamorphic rock derived from a basic igneous protolith
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define Migmatite
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a rock comprising a schistose or gneissose portion intimately mixed with veins of
apparently igneous quartzo-feldspathic material (leucosome). |
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define Mortar texture
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in mylonite, a matrix (mortar) of fine, syntectonically recrystallized material
enclosing larger, fractured, and strained relics (pophyroclasts) of pre-existing grains. |
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define Mylonite
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recrystallization in response to strain, typically in shear zones.
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define Orthogneiss
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a gneiss formed from an igneous protolith.
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define Paragneiss
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gneiss formed from a sedimentary protolith
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define pelite
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a metamorphic rock derived from a clay-rich sedimentary protolith.
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define pokiloblast
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a porphyroblast with a very high density of inclusions.
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define porphyroblast
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grains that are significantly larger than those of the matrix.
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define psammite
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a metamorphic rock derived from an arenaceous sedimentary protolith
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define psuedomorph
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a mineral, or aggregate of minerals, displaying the characteristic shape of
another mineral. Formed by the replacement of a primary mineral by a secondary mineral(s). |
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define pseudtachylyte
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a thin seam of glassy rock produced as the result of frictional heating during
extreme deformation in shear zones |
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define quartzite
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a metamorphic rock derived from a quartz-rich sedimentary protolith.
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define slate
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strongly cleaved rock with cleavage planes pervasively developed throughout the rock,
due to orientation of very fine grained phyllosilicate minerals. |
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define schist
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rock with parallel alignment of relatively coarse phyllosilicate grains, usually clearly
visible to the naked eye. |
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define symplectite
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an intimate intergrowth of two minerals, one having a worm-like habit.
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