Formation of metamorphic rocks

3.4 Metamorphic Rocks
Metamorphism – “to change form”
I. Formation of Metamorphic Rocks
- Most changes occur at high temperatures and pressures a
few km below the Earth’s surface.

Gneiss Rock


A. Contact Metamorphism –
hot magma moves into rock.

B. Regional Metamorphism –
results in large-scale
deformation and high-grade
metamorphism.


II. Agents of Metamorphism
*A.

Heat – The most important agent.
Provides the energy needed to
drive
chemical reactions.
- The heat comes from magma and the
change in
temperature with depth.
*B. Pressure (Stress) –
Causes a more compact
rock with greater density

Origin of Pressure in Metamorphism


•

III. Classification of Metamorphic
Rocks

Can be classified by texture and
composition.

A. Foliated Metamorphic Rocks - rock
has a layered or banded
appearance.
Ex: Gneiss & Schist.


Gneiss Typically Displays a
Banded Appearance


B. Nonfoliated Metamorphic Rocks –
- Does not have a banded texture.
- Most only contain one mineral.
Ex: Marble (calcite)
parent rock = limestone & Quartzite

Marble

Marble - A Nonfoliated
Metamorphic Rock




•

/>=home.gotoWebCode&wcprefix=cuk&wcsuffix=9999