GSU GEOL 1122K - CHAPTER 7 READING QUIZ (16 pages)

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CHAPTER 7 READING QUIZ



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CHAPTER 7 READING QUIZ

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Pages:
16
School:
Georgia State University
Course:
Geol 1122k - Introductory Geosciences Ii
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CHAPTER 7 READING QUIZ According to this metamorphic facies graph which of the following statements is TRUE Blueschist facies rocks form at high pressures and low temperatures Hornfels facies rocks form in a narrow range of temperature conditions 400 C Greenschist facies form at depths greater than 35 km The highest pressure facies indicated on this graph is the hornfels facies FEEDBACK Blueschist facies rocks do form under high pressure but low temperature conditions However hornfels facies rocks form under a wide range of temperatures greenschist facies form at depths less than 35 km and the highest pressure facies on this diagram is the eclogite facies Choose the listing that shows the rocks in increasing degrees of metamorphism i e from lower to higher grade migmatite metaconglomerate gneiss metaconglomerate gneiss migmatite gneiss metaconglomerate migmatite gneiss migmatite metaconglomerate FEEDBACK Metaconglomerate is barely metamorphosed see Fig 7 5c higher heat changes the rock into a gneiss Fig 7 6a and migmatite has been so strongly heated some rock has melted and become new igneous rock Identify the FALSE statement Hydrothermal fluids may consist of hot water gases or supercritical fluids can accelerate metamorphic reactions change a rock s chemical composition a process known as exhumation can be derived from groundwater or magma or can be the product of metamorphic reactions FEEDBACK They do change the chemical composition but the process is known as metasomatism Exhumation means that deeply buried rocks can eventually be exposed at Earth s surface Metamorphic aureoles typically contain nonfoliated rock like hornfels because they form adjacent to an intruding pluton which provides heat for metamorphism they form as a consequence of shearing without a subsequent change in temperature or pressure compressional forces associated with mountain building provide the necessary pressure to create hornfels they form at shallow burial depths less than 8 km FEEDBACK Aureoles typically form around igneous intrusions by contact thermal metamorphism The addition of heat but little pressure produces nonfoliated metamorphic rocks Quartzite is basically a solid mass of interlocking quartz grains breaks around the separate grains of quartz that make it up is always either white or gray always shows strong compositional banding FEEDBACK Quartzite is a nonfoliated no banding metamorphic rock that may be white gray purple or green it breaks across not around its component grains Recrystallization occurs when rocks become warm enough that they behave like soft plastic results in the growth of new minerals that differ from the protolith changes the texture shape and size of the grains is a process by which grains push against one another creating dissolution FEEDBACK The recrystallization process doesn t change the identity or chemical composition of the mineral it just produces larger crystals of the mineral so it changes the texture of the grains Plastic deformation occurs when rocks behave like soft plastic neocrystallization forms new minerals that differ from the protolith and pressure solution occurs when grains push against each other and cause dissolution Tension a type of stress is created by a pull perpendicular to a surface is the reason a balloon collapses when you take it to the bottom of a pool occurs when rocks move sideways relative to each other is a compression exerted equally from all sides FEEDBACK Tension is a stress created by pulling perpendicular to a surface such as grabbing two ends of a piece of taffy and pulling your hands apart A balloon collapses in a pool because of pressure shear occurs when rocks move sideways and pressure again occurs when compression is exerted equally from all sides What is the protolith of marble quartz sandstone limestone phyllite gypsum FEEDBACK A protolith is the parent rock that is metamorphosed into a different rock metamorphosed limestone is marble What type of foliation does slate a common material used for roof shingles exhibit banding cleavage schistosity metamorphic differentiation FEEDBACK Slate is used in roofing because its slaty cleavage causes it to break in regular thin sheets see Fig 7 4 Which is NOT a common process by which metamorphic rocks are formed pressure solution plastic deformation schistosity recrystallization FEEDBACK Schistosity is not a process it is the type of foliation in schists that results from the preferred orientation of large mica flakes Which of the following does NOT describe a change induced on protolith rocks due to mountain building as a result of convergent margin tectonics and continental collision Surface rock is sent to great depths beneath the new mountain belt The once surface rock heats up due to igneous activity and the geothermal gradient Hot magma rising beneath the converging continents heats seawater which then rises through the crust to react with the surface rocks Compression and shearing metamorphose the once surface rock FEEDBACK During hydrothermal metamorphism at mid ocean ridges hot magma rises beneath the ridge axis where it heats seawater to create hydrothermal fluids but this does not happen during mountain building Which of the following is NOT a common metamorphic facies greenschist blueschist granulite mafic FEEDBACK The term mafic refers to minerals and or rocks that are high in iron and magnesium it does not refer to a metamorphic facies See Box 7 1 for further explanation of each facies and formation conditions Which of the following locations could not possibly be part of a shield Hawaii Canada Northern Europe Siberia FEEDBACK Shields are the oldest areas of Earth s surface Hawaii is a recently formed hotspot island Which of the following metamorphic processes is depicted in this before left and after right image where spherical grains dissolve on the sides that undergo significant pressure and new mineral material precipitates where the pressure is low plastic deformation recrystallization neocrystallization pressure solution FEEDBACK This image shows the process of pressure solution Grains that were once spherical dissolve on the sides experiencing pressure where they push against neighboring grains The dissolved ions migrate away and new minerals precipitate in the regions of low pressure Which of the following rocks is classified as nonfoliated hornfels phyllite slate schist FEEDBACK Hornfels is a nonfoliated metamorphic rock because it was formed in the


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