Metamorphism, metamorphic rocks

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

Non-foliated Metamorphic Rocks

Slate

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