Metamorphism, Metamorphic Rocks

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Lecture 8 Metamorphism, Metamorphic
Rocks and Hydrothermal Rocks
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Physical Geology
Lecture Outline
I Definitions II Controls on Metamorphic
Characteristics A) Composition of Parent
Rock B) Temperature C) Pressure i. Differenti
al Stress ii. Foliation D) Fluids E) Time III
Types of Metamorphism A) Contact
Metamorphism B) Regional Metamorphism IV Plate
Tectonics and Metamorphism
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Physical Geology
Definitions
metamorphism - the mineralogical, chemical, and
structural adjustment of solid rocks to physical
and chemical conditions imposed at depth below
the surface zones of weathering and cementation,
which differ from the conditions under which the
rock originated.
metamorphic rock - any rock derived from
pre-existing rocks by mineralogical, chemical,
and/or structural changes, essentially in the
solid state, in response to marked changes in
temperature, pressure, shearing stress, and
chemical environment, generally at depth in the
Earth's crust.
parent rock - the original rock from which a
metamorphic rock was formed. Parent rocks may be
igneous, sedimentary, or metamorphic.
metamorphic grade - the intensity of
metamorphism, measured by the degree of
difference between the parent rock and the
metamorphic rock.
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Physical Geology
Metamorphic Rocks
Foliated Metamorphic Rocks
Non-foliated Metamorphic Rocks

• Slate
• Phyllite
• Schist
• Gneiss

• Anthracite Coal
• Hornfels
• Marble
• Quartzite
• Serpentinite
• Soapstone

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Physical Geology
Controls on Metamorphic Characteristics

• Composition of Parent Rock
• Temperature
• Pressure
• Fluids
• Time
• Tectonic Setting

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Physical Geology
Controls on Metamorphic CharacteristicsParent
Rock
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Physical Geology
Controls on Metamorphic CharacteristicsTemperatur
e
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Physical Geology
Controls on Metamorphic CharacteristicsPressure
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Physical Geology
Controls on Metamorphic CharacteristicsPressure
- Foliation
foliation - the planar structure that results
from the flattening of the constituent grains
of a metamorphic rock
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Physical Geology
Controls on Metamorphic Characteristics T-P
Diagram
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Physical Geology
Controls on Metamorphic Characteristics Temperatur
e and Pressure
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Physical Geology
Controls on Metamorphic CharacteristicsFluids

• water and carbon dioxide most common metamorphic
  fluids
• present along grain boundaries or in pore spaces
  of rocks
• Fluids derived from several sources
• trapped in pore spaces when parent rock formed
• exuded from magmas
• dehydration of water bearing minerals (e.g.
  gypsum, clays)
• metamorphic reactions themselves may liberate
  fluids
• often contain ions in solution, increasing the
  rate of chemical reactions

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Physical Geology
Types of Metamorphism

• Contact Metamorphism
• Regional Metamorphism
• Hydrothermal Metamorphism
• Burial Metamorphism
• Blueschist Metamorphism
• Eclogite Metamorphism

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Physical Geology
Types of MetamorphismContact Metamorphism
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Physical Geology
Types of MetamorphismRegional Metamorphism
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Physical Geology
Types of MetamorphismProgressive Metamorphism
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Physical Geology
Types of MetamorphismHydrothermal Processes
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Physical Geology
Types of MetamorphismHydrothermal Processes
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Physical Geology
Types of MetamorphismHydrothermal Processes -
Metasomatism
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Physical Geology
Types of MetamorphismHydrothermal Processes -
Veins
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Physical Geology
Metamorphism and Plate Tectonics
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Physical Geology
Physical Geology
Metamorphism and Plate TectonicsMetamorphic
Facies