METAMORPHIC ROCKS

Rocks that form from other pre-existing rock (sedimentary, igneous, or metamorphic) that have been changed from high temperature and/or high pressure

Metamorphic Rocks

Metamorphic Rocks Formation

Conditions that cause rock to undergo metamorphism include:

• Heat - Under conditions of high temperature from magma contacting pre-existing rock.• Pressure - Deep burial and pressure from mountain formation.

Types of Metamorphism

1. Contact Metamorphism

2. Regional Metamorphism

Contact Metamorphism

Deep burial and pressure from mountain formation.

The main metamorphic agent is heat.

Also forms when pre-existing rock comes into contact with molten lava or magma. The heat from the molten material is hot enough to cause the minerals in the original rock to re-crystallize, but not melt.

Regional Metamorphism

Covers large areas typically associated with mountains

Deep burial and pressure from mountain formation.

Heat and Pressure change the rock

Types of Metamorphic Rocks

Foliated: rocks with mineral crystals arranged in cable-like distorted layers/structures Mineral Alignment Banding Animation: Foliation

Nonfoliated: rocks with recrystallized minerals; no layering Recrystallization: This is the growth of new

mineral crystals from other rocks.

Texture Composition Type of Metamorphi

sm

Comment Rock Name

MicaRegional

(Heat and Pressure increase w/ depth)

Low-Grade metamorphism of

SHALE

Mica, Quartz, Feldspar,

Amphiboles, Garnet

Foliation surfaces shiny from microscopic mica

crystals

Mica, Quartz, Feldspar,

Amphiboles, Garnet, Pyroxene

Platy mica crystals visible

Mica, Quartz, Feldspar,

Amphiboles, Garnet, Pyroxene

Compact, may split easily

FOLI

ATED

MIN

ER

AL

ALI

GN

MEN

TB

AN

D-

ING

Scheme for Metamorphic Rock Identification

Slate

Phyllite

Gneiss

Schist

Progression of Metamorphism

Start with a shale and then hitit with heat and pressure!

Rock Name Rock Type Grade of Metamorphism

Shale Sedimentary

-----

Slate Metamorphic

Low

Phyllite Metamorphic

Low/Intermediate

Schist Metamorphic

Intermediate/High

Gneiss Metamorphic

High

Molten Rock Cools into Igneous Rock

-----

MoreHeat

&Pressure

Shale(Sedimentary Rock)

Slate(Metamorphic Rock)

Heat&

Pressure

Slate(Metamorphic Rock)

Heat&

PressurePhyllite

(Metamorphic Rock)

Phyllite(Metamorphic Rock)

Schist(Metamorphic Rock)

Heat&

Pressure

With even more heat & pressure(High-Grade Metamorphism)

… you end up with something that is really Gneiss!

Scheme for Metamorphic Rock Identification

Texture

Composition Type of Metamorphi

sm

Comment Rock Name

Variable Contact(Heat)

Various rocks changed by nearby

magma/lava

QuartzMetamorphism of Quartz

Calcite and/or Dolomite

Metamorphism of

Various minerals in particles and

matrix

Pebbles may be distorted or stretched

NO

NFO

LIA

TED

Regional

(Heat&

Pressure)

Sandstone

Limestone orDolostone

Hornfels

Quartzite

Marble

Metaconglomerate

ESRT p. 7

Animation: Metamorphic Rock Scheme

Where are metamorphic rocks found?

At the interface between igneous and sedimentary rocks

• Mountainous regions

THE ROCK CYCLEHow are rocks classified?

How are rocks classified?

By their origin (the way they are formed)

Major Rock Groups

Sedimentary Formed at the Earth’s surface Clastic (Mineral Fragments or grains, clays) Crystalline (chemical precipitates and

evaporites) Bioclastic (formed organically from shells or

plants) Igneous

Formed from magma (molten rock) Plutonic (intrusive):slow cooling, coarse/very

coarse crystals Volcanic (extrusion): quick cooling at the

surface, glassy/fine crystals Metamorphic

Changed by heat and pressure

Rock Cycle Conclusion

Fig. 2.9

MAGMA

MAGMA

Solidification

IGNEOUS

MAGMA

IGNEOUS

Plutonic

Solidification

MAGMA

Volcanic

IGNEOUS

Plutonic

Solidification

MAGMA

Volcanic

IGNEOUS

Plutonic

Uplift

Solidification

Weathering & Erosion

MAGMA

Volcanic

IGNEOUS

Plutonic

SEDIMENT

Solidification

Weathering & Erosion

SEDIMENT

MAGMA

Volcanic

IGNEOUS

Plutonic

SEDIMENT

SEDIMENTARY

Solidification

Weathering & Erosion

Erosion

Transport

Deposition

MAGMA

Volcanic

IGNEOUS

Plutonic

SEDIMENT

SEDIMENTARY

Solidification

Weathering & Erosion

Deposition

Burial/Compaction

Cementation

MAGMA

Volcanic

IGNEOUS

Plutonic

SEDIMENT

SEDIMENTARY

METAMORPHIC

Increased P&T

Solidification

Weathering & Erosion

Deposition

Burial/Compaction

Cementation

MAGMA

Volcanic

IGNEOUS

Plutonic

SEDIMENT

SEDIMENTARY

METAMORPHIC

Increased P&T

MeltingSolidification

Weathering & Erosion

Deposition

Burial/Compaction

CementationCan you see

any shortcuts?

MAGMA

Volcanic

IGNEOUS

Plutonic

SEDIMENT

SEDIMENTARY

METAMORPHIC

Increased P&T

MeltingSolidification

Weathering & Erosion

Deposition

Burial/Compaction

Cementation

MAGMA

Volcanic

IGNEOUS

Plutonic

SEDIMENT

SEDIMENTARY

METAMORPHIC

Increased P&T

MeltingSolidification

Weathering & Erosion

Deposition

Burial/Compaction

Cementation

Citations Slide 6 (Progression of Metamorphism of Shale)

http://physics.uwstout.edu/geo/_derived/sect4.htm_txt_sect4.2.gif Slide 10

Shale:

http://library.thinkquest.org/06aug/02459/rocks/sedimentary/Shale.jpg Slate:

http://www.global-b2b-network.com/direct/dbimage/10260661/Grey_Slate.jpg Slide 11:

Phyllite:

http://www.bedford.k12.ny.us/flhs/science/geoscience/images/phyllite.jpg Slide 12:

Schist (1)

http://www.randall.k12.wi.us/rocks/images/schist-with-garnet.jpg Schist (2)

http://www.es.ucl.ac.uk/schools/Glossary/schist.jpg Slide 13:

Gneiss (1)

http://hyperphysics.phy-astr.gsu.edu/hbase/geophys/geopic/gneiss2.jpg Gneiss (2)

http://www.cropsoil.uga.edu/soilsandhydrology/images/Gneiss.jpg Gneiss (3)

http://upload.wikimedia.org/wikipedia/commons/6/60/Gneiss.jpg Slide 16:

8/16/2006 Physical Setting Regents Earth Science Exam p. 18 Slide 17:

Earth Science Reference Tables p. 6