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Published byJena Weddington Modified over 10 years ago
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“If something is gneiss, don’t take it for granite.”
Metamorphic Rocks “If something is gneiss, don’t take it for granite.”
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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
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