Lecture 8
Metamorphism, Metamorphic Rocks
and
Hydrothermal Rocks
Physical Geology
Lecture Outline
I
II
A)
B)
C)
Definitions
Controls on Metamorphic Characteristics
Composition of Parent Rock
Temperature
Pressure
i.
ii.
Differential Stress
Foliation
D)
E)
Fluids
Time
A)
B)
Contact Metamorphism
Regional Metamorphism
III
IV
Types of Metamorphism
Plate Tectonics and Metamorphism
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.
Physical Geology
Metamorphic Rocks
Foliated Metamorphic Rocks
Slate
Non-foliated Metamorphic Rocks
Anthracite Coal
Phyllite
Hornfels
Schist
Marble
Gneiss
Quartzite
Serpentinite
Soapstone
Physical Geology
Controls on Metamorphic Characteristics
Composition of Parent Rock
Temperature
Pressure
Fluids
Time
Tectonic Setting
Physical Geology
Controls on Metamorphic Characteristics
Parent Rock
Physical Geology
Controls on Metamorphic Characteristics
Temperature
Physical Geology
Controls on Metamorphic Characteristics
Pressure
Physical Geology
Controls on Metamorphic Characteristics
Pressure - Foliation
foliation - the planar structure that results from the flattening of the constituent
grains of a metamorphic rock
Physical Geology
Controls on Metamorphic Characteristics
T-P Diagram
Physical Geology
Controls on Metamorphic Characteristics
Temperature and Pressure
Physical Geology
Controls on Metamorphic Characteristics
Fluids
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
Physical Geology
Types of Metamorphism
Contact Metamorphism
Regional Metamorphism
Hydrothermal Metamorphism
Burial Metamorphism
Blueschist Metamorphism
Eclogite Metamorphism
Physical Geology
Types of Metamorphism
Contact Metamorphism
Physical Geology
Types of Metamorphism
Regional Metamorphism
Physical Geology
Types of Metamorphism
Progressive Metamorphism
Physical Geology
Types of Metamorphism
Hydrothermal Processes
Physical Geology
Types of Metamorphism
Hydrothermal Processes
Physical Geology
Types of Metamorphism
Hydrothermal Processes - Metasomatism
Physical Geology
Types of Metamorphism
Hydrothermal Processes - Veins
Physical Geology
Metamorphism and Plate Tectonics
Physical Geology
Metamorphism and Plate Tectonics
Metamorphic Facies