Metamorphic Rocks “If something is gneiss, don’t take it for granite.”
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Transcript of Metamorphic Rocks “If something is gneiss, don’t take it for granite.”
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Metamorphic Rocks
“If something is gneiss, don’t take it for granite.”
![Page 2: Metamorphic Rocks “If something is gneiss, don’t take it for granite.”](https://reader035.fdocuments.in/reader035/viewer/2022081421/56649cb75503460f9497c4d2/html5/thumbnails/2.jpg)
![Page 3: Metamorphic Rocks “If something is gneiss, don’t take it for granite.”](https://reader035.fdocuments.in/reader035/viewer/2022081421/56649cb75503460f9497c4d2/html5/thumbnails/3.jpg)
Metamorphic Agents
• Pressure (>1,000 times atmospheric pressure)
• Temperature (>300 degrees C)
• Chemical Fluids (mineral saturated hot water)
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Metamorphic Environments
• Contact (thermal) – intrusion by magma
• Hydrothermal – ion-rich hot water circulates through cracks
• Mountain Building – regional metamorphism
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Metamorphic Changes -Rocks adjust to new conditions by:
• Changes in texture
• Changes in mineralogy
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Changes in Texture
• Compaction
• Recrystallization - may cause – Foliation– Lineation
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Changes in Minerology
• Recrystallization – small crystals reform into larger crystals of the same mineral
• Formation of new minerals – elements recombine to form new minerals– Garnet, Chlorite and others found only (or
mostly) in metamorphic rock
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Grades of Metamorphosis
• Low Grade – Low temperature and pressure results in slate and phyllite
– “Rock cleavage” in slate– Foliated– Fine grained– Slate looks dull, phyllite is shiny
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Grades of Metamorphosis (cont.)
• Intermediate Grade – higher temperatures and pressures than Low Grade– Schist
• Foliated
• Mica, garnet
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Grades of Metamorphosis (cont.)
• High temperatures and pressures– Gneiss and Migmatite
• Dark & light banding of mica (dark), quartz & feldspar (light)
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Foliated Metamorphic Rock Sequence
• Slate – parent rock is shale (sedimentary)
• Phyllite – parent rock is slate
• Schist – parent rock is phyllite
• Gneiss – parent rock is schist
• Migmatite – parent rock is gneiss
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Non-Foliated Metamorphic Rocks & Their Parent Rocks
• Marble – Parent rock is limestone or dolostone (calcite, reacts with acid)
• Quartzite – Parent rock is sandstone
• Anthacite – Parent rock is bituminous coal
• Hornfels – Parent rock is any rock type
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Metamorphic Rock Dichotomous Key
Proceed to Dichotomous Key Activity
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View in slide show, then click to view:
Dichotomous Metamorphic Key