Class Notes

Metamorphismand Metamorphic Rocks

METAMORPHISM

The solid-state change in composition, mineralogy, or texture of pre-existing rocks due to the change in temperature, pressure, or chemical components.

AGENTS OFMETAMORPHISM

1) _______________

a)___________________

b)___________________

2)___________

3)_____________________

Pressure vs. Depth figure (GEODe)

Confining vs. Directed Pressure (fig. 8.4)

Temperature vs. Depth figure (GEODe)

Geothermal Gradient Figure (fig. 8.3)

Typical Geothermal Gradients (you draw)

Metamorphic Grade (you draw)

Main types of Metamorphism

1)_____________

2)_____________

3)_____________

_______________Metamorphism:

Changes caused by the high temperature and directed pressures associated with regional mountain building.

______________Metamorphism:

Changes caused by the high temperature of an intruding magma, which can “bake” the surrounding rock.

______________Metamorphism

Changes caused by interaction of hot, chemically rich fluids with surrounding rock.

How are Metamorphic Rocks Classified?

1)_________________

a)__________________

b)__________________

2)______________________

Examples of Non-foliated and Foliated Textures

____________________: The parallel alignment of recrystallized minerals.

Typically the result of ________________________

Q. How does metamorphic foliation form?

A.

Types of Metamorphic Foliation

1)______________

2)______________

3)______________

Types Metamorphic Foliation:

______________:tendency to split along parallel planes

______________:elongate and platy minerals recrystallize along parallel planes

______________:dark and light-colored minerals segregate into compositional bands

Examples of Foliated Metamorphic Rocks

1) _______________

2)________________

3)________________ e.g.

4)_________________

Metamorphism of Shale (sedimentary rock) to Slate (low-grade metamorphic rock)

Development of Slatey Cleavage (fig. 8.8)

Q. What is the difference between bedding and foliation?

A.

Shale and Phyllite (fig. 8.14)

Increasing grade (intensity) of metamorphism results in increasing ________________.

e.g.Slate – Phyllite – Schist

Q. What is a phyllite?

A.

Q. What is a schist? (fig. 8.11)

A.

Q. What is a gneiss? (fig. 8.10)

Compare a Granite with a Gneiss.

Classification of Foliated Metamorphic Rocks (fig. 8.12)

How do metamorphic rocks change with progressively intense metamorphism? (fig. 8.24)

_____________________ Metamorphism:

Changes caused by the high temperature of an intruding magma, which can “bake” the surrounding rock.

The area adjacent to an intrusive that has been altered by contact metamorphism (i.e. the “baked rim”) is called the: _________________________ (see fig. 8.19)

Examples of Non-Foliated Metamorphic Rocks

1)Marble*

2)Quartzite*

3)Hornfels*

4)Anthracite

* = ?

Marble (fig. 8.17) and Quartzite (fig. 8.18) in hand specimen and in thin section.

Classification of Nonfoliated Metamorphic Rocks (fig. 8.12)

How do Metamorphic and Sedimentary and Igneous textures differ?

_________________ Metamorphism:

Changes caused by interaction of hot, chemically rich fluids with surrounding rock.

e.g. Hydrothermal metamorphism at mid-ocean ridges. (fig. 8.20)

e.g. Hydrothermal fluids associated with intrusive bodies (GEODe).

Some minerals formed mainly from hydrothermal alteration include:

_____________________are minerals which form under a relatively restricted range of pressure and temperature (i.e. act as “paleo-thermometers and barometers”)

They are commonly used to define the:

Mineralogic changes in metamorphosed shales (fig. 8.25)

Metamorphic Zones in New England (fig. 8.26)

A____________________________ is an assemblage of rocks with characteristic minerals formed under specific temperature & pressure conditions

Be able to locate (or sketch) the following on a Temperature-Depth diagram:

Hornfels facies

Blueschist facies

Greenschist facies

Amphibolite facies

Compare metamorphic facies associated with

1) contact metamorphism

2) regional mountain building

3) subduction

Migmatites form by what process?

The_____________ is the rock that was metamorphosed to form a metamorphic rock (i.e. the Parent Rock)

Examples

Marble ------>?

Quartzite --->?

Anthracite--->?

Slate --------->?

Gneiss ------->?

Gneiss ------->?

How does metamorphism differ in different plate tectonic settings? (e.g. fig. 8.28)