Download Metamorphic Rocks

Metamorphic Rocks
Metamorphic rocks are:
the result of the
application of heat,
pressure and directed
stress, or some
combination of these
effects applied to preexisting rock of any type.
The process by which
metamorphic rocks are
produced is called
metamorphism.
Gneiss
Slate
Metamorphic Rocks

2 TYPES OF TEXTURES – FOLIATED
AND NON-FOLIATED


Foliated = banded rock, minerals are
arranged in bands, or thin sheets/layers
Non-foliated = unbanded rock, usually
consist of all one type of mineral so may
appear to have a granular or uniform texture

Ex.) quartz (sand grains) makes up quartzite,
calcite (limestone) makes up marble
Foliated –vs- Non-foliated
Metamorphic Textures
Foliated – looking at thin
section under microscope
Non-foliated – looking at thin
section under microscope
Foliated Texture

Forms when minerals (many of which are platy micas
such as biotite and muscovite) line up producing a
distinct layering in the rock.

Minerals tend to line up perpendicular to the
pressure
Foliated Texture
Foliated Texture
The layering of minerals produces three distinctly different looking rocks,
those with slaty cleavage (e.g. slate), schistosity (e.g. schist), and
mineral banding (or gneiss texture).
Changes undergone to rocks during
metamorphism
Slaty Cleavage Foliation
Slate
Phyllite
Phyllite
Schistosity Foliation
Mica Schist
Garnet Schist
Schist
Banding in Foliation
Gneiss

TYPES OF METAMORPHISM:


REGIONAL – large scale metamorphism
(over large areas , up to thousands of
square feet) – think mountains
LOCAL – smaller scale metamorphism
 Contact – think burn on
your finger
 Deformational/Dynamic
think bent finger – smashed
in the door
–
Types of Metamorphism
( T, P)

Regional Metamorphism
Occurs during mountain building
 On a large scale (over large
areas)



Forms most of the
metamorphic rocks of Earth’s
crust
Rocks are subject to high heat and
high pressure
The result is a rock that has
pronounced foliation and layering.
(The foliation is usually perpendicular
to the direction of the applied stress.)
( T)

Local Metamorphism –
Contact
Occurs on a smaller scale

when hot magma (liquid
and gases) move into the
parent/country rock,
heating and changing it. (so
its close to magma)

Usually non-foliated and
appear to have a sugary
texture
( T, P)

Local Metamorphism –
Deformational/Dynamic
Occurs on a smaller scale
 in fault zones (so
friction & pressure
change the rock)
 Can have sugary texture
(non-foliated) or be
foliated
Examples of Metamorphic Rocks

Quartzite – parent rock is Sandstone
Examples of Metamorphic Rocks

Marble – parent rock is Limestone
Examples of Metamorphic Rocks

Slate – parent rock is Shale
Examples of Metamorphic Rocks

Phyllite – parent rock is Shale
Examples of Metamorphic Rocks

Schist – parent rock is Shale (sometimes
granite or other rocks, depending on the
content)
Mica Schist
Garnet Schist
Examples of Metamorphic Rocks

Gneiss – parent rock is Shale, Granite, or
conglomerate (sometimes other rocks,
depending on the content)
(Metamorphic Website)