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94 Cards in this Set
- Front
- Back
plane of the ecliptic
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earth's axis tilted at about 23.5 degrees to the plane in which it orbits the sun
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principle of uniformitarianism
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most ancient geologic features are formed by the same processes as modern ones
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pressure
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the pull on earth's gravity
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hydrostatic pressure
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pressure due to the weight of water
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lithostatic pressure
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pressure due to the weight of overlying rock
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asthenosphere
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zone in the upper mantle that has low rigidity and flows like soft plastic
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triple junction
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when three plates come together
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element
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a substance that cannot be broken down chemically into other substances
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atom
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the smallest piece of an element that still has all the properties of that element
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compounds
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atoms that combine with one another chemically
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molecule
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smallest possible piece of a compound
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cryosphere
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sphere made up with frozen water
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geosphere
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sphere made up of the solid earth
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bedrock
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a solid aggregate of minerals and rocks attached to those below
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sediment
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unattached boulders, sand, and clay
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soil
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sediment and rock modified by interactions with the atmosphere, hydrosphere, and organisms so that it can support plant life
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flux
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movement of materials from one reservoir to another
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heat energy
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measure of the degree to which atoms or molecules move about in matter
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density
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mass / volume (mass over volume)
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geobaric gradient
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rate at which lithostatic pressure increases
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lithosphere
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earth's crust to 100-150km of the mantle and is relatively rigid and is the outermost layer
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active continental margin
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where earthquakes and volcanic eruptions are common (US west coast)
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passive continental margin
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where earthquakes and volcanic eruptions are not common (US east coast)
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mineral
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naturally occurring, homogeneous, inorganic solid with an ordered internal arrangement of atoms and a distinctive chemical composition
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grain
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an irregular piece of mineral
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rock
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naturally occurring, inorganic solid consisting of an aggregate of mineral grains, pieces of older rocks, or a mass of natural glass
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luster
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the way light interacts with a mineral's surface
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crystal habit
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preferred crystal shape that forms when it grows unimpeded by other grains
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fracture
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occurs when there are no zones of particularly weak bonding within a mineral
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cleavage
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occurs when bonds holding atoms together are weaker in some directions than in others
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specific gravity
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a comparison of its density with the density of water
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elastic
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return to their original, unbent shape
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flexible
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retain their new shape
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rock composition
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the identity of minerals or glass that make up a rock
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rock texture
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the dimensions and shape of grains and the way in which grains are arranged, oriented, and held together
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igneous rocks
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form through the cooling and solidification of molten rock, which is created by the melting of preexisting rock in the mantle or lower crust
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sedimentary rocks
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form at or near the surface of the earth in two ways: when grains of preexisting rocks accumulate or when minerals precipitate out of water
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metamorphic rocks
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form when preexisting rocks are subjected to physical and chemical conditions within the earth that are significantly different from those under which they first formed
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course sized
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grains big enough to be identified easily
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medium sized
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grains can be seen as separate grains but can't be easily identified
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fine sized
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grains can barely be recognized
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very fine sized
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grains are so small they cannot even be seen with a magnifying glass
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equant
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grains have the same dimension in all directions
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inequant
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grain dimension in different directions is different
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crystalline texture
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crystallizing minerals interfere with one another and interlock
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foliation
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if the grains are aligned parallel to one another
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plutons
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massive intrusive blobs
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dikes
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intrusions that form thin sheets cutting across layering in the wall rock
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sills
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intrusions that form thin sheets parallel to the layers of wall rock
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viscosity
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ability to flow
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phaneritic texture
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texture of igneous rocks with coarse grains
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aphanitic texture
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texture of igneous rocks with fine grains
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porphyritic texture
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texture of igneous rocks with two different grain sizes
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pyroclastic debris
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enormous amounts of material blasted into the air by volcanic eruptions
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ash fall
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fine grain volcanic debris that falls quietly and blankets the ground
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pyroclastic flows
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avalanches of ash that rush down the side of a volcano while so hot that the fragments weld together immediately to form rock
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felsic igneous rocks
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have the most silica and the least iron and magnesium, contain a lot of potassic feldspar and plagioclase, light colored, low specific gravity
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intermediate igneous rocks
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between felsic and mafic rocks
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mafic igneous rocks
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have less silica and sodium but more calcium, iron, and magnesium, dark green or black, high specific gravities
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ultramafic igneous rocks
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least silica and most iron and magnesium, very dark colored and have the highest specific gravities
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decompression melting
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once pressure decreases, the heat already present in the rock is sufficient to overcome the bonds and cause melting
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flux melting
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water and volatiles are released when the subducted plate reaches critical depth and rise into the asthenosphere where they help melt the asthenosphere in
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heat transfer melting
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some very hot magmas that rise into continental crust from the mantle bring enough heat to start melting the crust
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partial melting
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magmas form by melting some of the preexisting rock
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magmatic differentiation
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early formed minerals may separate from a magma, usually by sinking, because they are denser than the liquid
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assimilation
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as a magma rises, it may add ions by melting some of the surrounding rocks
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magma mixing
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intermediate rocks crystallize from this magma which is when felsic and mafic magmas mix
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mineralogically immature
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sediments that still contain nonresistant minerals and rock fragments
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mineralogically mature
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sediments in which all minerals have weathered to produce stable minerals
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lithification
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accumulations of clasts that are buried and the weight of overlying sediment squeezes out air and water, fitting the clasts more tightly together
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cementation
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when ion rich groundwater passes through the compacted sediment, minerals precipitate and bind the clasts together
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diagenesis
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any chemical or physical change that happens in a sedimentary environment subsequent to the original deposition of the sediment
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biogenic sedimentary rock
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rock composed primarily of the remains of living organisms
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sorting
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the measure of the uniformity of grain size in clastic sedimentary rocks
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beds
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layers of sediment
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graded beds
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layers in which the clast size decreases progressively from the bottom to the top
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asymmetric ripply marks
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have systematically oriented steep and gentile sides and are produced by a current that flowed from the gentle side toward the steep side
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symmetric ripple marks
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have steep slopes on both sides and form from oscillating currents
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cross beds
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subtle curving surfaces that lie at an angle to the main bedding surfaces and form when sediment moves up the up-current side and then slips down the lee side as dunes and ripples build
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protolith
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metamorphic rock parent rock
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diffusion
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when freed atoms migrate slowly through the solid rock
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differential stress
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the type of pressure in such rock due to squeezing and/or shear as directed pressure; can flatten or elongate them rock on one direction
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metasomatism
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when the chemical composition of a metamorphic rock changes significantly due to the reaction with hydrothermal fluids
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contact metamorphism
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occurs where rocks are subjected to elevated heat without a change in pressure and without the application of differential stress; happens where an igneous rock comes in contact with a rock
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regional metamorphism
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occurs where rocks in a large region of crust are subjected to increases in temperature and pressure and are subjected to differential stress; happens during mountain building processes
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burial metamorphism
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happens when rocks are buried very deeply by overlying sediment
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dynamic metamorphism
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occurs where rock undergoes differential stress in response to shear along a fault zone but does not undergo a change in temperature or lithostatic pressure
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preferred orientation
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the alignment of parallism of grains
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granoblastic texture
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metamorphic rocks with random grain orientations
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mylonite
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a very fine grained rock with a strong foliation and lineation
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porphyroclasts
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leftover grains of feldspar
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metamorphic grade
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the approximate degree to which a rock has changed during dynamothermal or thermal metamorphism
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porphyroblasts
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large grains grown during metamorphism
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gneissic texture
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compositional banding, defined by the alternation of light colored and dark colored layers
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