Metamorphic Rocks

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Metamorphic Rocks

• If something is gneiss, dont take it for
  granite.

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(No Transcript)
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Metamorphic Agents

• Pressure (gt1,000 times atmospheric pressure)
• Temperature (gt300 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