Metamorphism & Metamorphism & Metamorphic RocksMetamorphic RocksMetamorphism & Metamorphism &

Metamorphic RocksMetamorphic Rocks

The rock that forms depends on:

How do Metamorphic rocks form?How do Metamorphic rocks form?

Why Should Why Should YouYou Study Metamorphic Study Metamorphic Rocks?Rocks?

What are the 3 Agents of Metamorphism?What are the 3 Agents of Metamorphism?

Heat Heat ______________________ the the raterate of chemical reactions. of chemical reactions.

Sources of Heat:Sources of Heat:

How does TIME affect transformations?How does TIME affect transformations?

LithostaticLithostatic

Differential __________:Differential __________:

Chemically Active Fluids

Sources of fluids:Sources of fluids:

1)1) ..

2)2) ..

3)3) ..

Types of MetamorphismTypes of Metamorphism

Regional Metamorphism

Contact MetamorphismContact Metamorphism

Alteration occurs because:

Aureole

Width determined by:

Index Minerals

Mylonites

Dynamic / Cataclastic Metamorphism

How Are Metamorphic Rocks How Are Metamorphic Rocks Classified?Classified?

Two Groups

foliation

Foliated Meta. Rocks Rock Typical Meta. Features Parent Rock Typical Meta. Features Parent

Name Minerals Grade of Rock RockName Minerals Grade of Rock RockSlateSlate clays, micas, clays, micas, low low fine-grained, shale, fine-grained, shale,

chloritechlorite splits uniformly vol. ash splits uniformly vol. ashPhyllitePhyllite quartz, micas, quartz, micas, low-med fine-gr, glossy shale low-med fine-gr, glossy shale

chloritechlorite “crinkled” “crinkled”

Schist micas, chlorite, med-high distinct foliation shale, talc, garnet visible carbonates, hbl

basalt/gabbroGneiss qtz, feldspar, high light & dark shale, hbl, micas bands sandstone, basalt/gabbro felsic ign.

Amphibolite hbl med-high dark, weak fol. basalt/gabbro

Migmatite qtz, feldspar, very granite streaks felsic ign. & hbl, mica high in gneiss sed. mixed

SLATE

(very fine-grained, foliated) • formed by ____________, ___________ metamorphism • • used for

PHYLLITE

(fine-grained, foliated)

• glossy sheen

• coarser-gr. than slate

• “crinkled” appearance

SCHIST(medium-grained, foliated)

• platy/elongate minerals

• _________________________ metamorphism Schistose foliation

GNEISS

(medium-grained, foliated)

• ______________• ________________________ metamorphism

• Light bands granular minerals. (______________________)

• Dark bands platy/elongate min. (______________________)

AMPHIBOLITE (med-gr, foliated) hornblende & plagioclase (___________________ regional meta.)

MIGMATITES (mixed rocks) • _________________________ metamorphism

• High-grade meta. rx intermix w/ streaks of granite.

Georgian Bay, Ontario, Canada

Nonfoliated Metamorphic Rocks

Nonfoliated Meta. Rocks

Rock Typical Meta. Features Parent Name Minerals Grade of Rock RockMarble calcite, low-high interlocking limestone,

dolomite grains dolostone Quartzite quartz med-high interlocking quartz

grains, hard sandstoneGreenstone chlorite, epidote, low-high fine-grained mafic ign.

hornblende green color

Hornfels micas, garnet, low-med fine-grained, mudrocks quartz hard, dense Anthracite carbon high black, lustrous, coal

subconchoidal fracture

Marble

• ________________________________ metamorphism

• Parent Rock =

How is Marble used?

metamorphism

C

QUARTZITE

• _____________________________________ metamorphism

• Parent Rock = ________________________

• Hard & compact w/ uniform strength [breaks across grains rather than around them]

• used in __________________________________________

metamorphism

Greenstone (____________________ meta)

• Parent rock = ________________________ (green color from chlorite, epidote, & hornblende)

Hornfels (__________________________ meta)

• Parent rock = __________________________

• equidimensional grains

Anthracite

• Parent rock = ___________________________

Isograd

What Are Metamorphic Zones?

Does Metamorphism Relate to Plate Tectonics?

Low-temp/high-press _______ part of subducting plate High-temp./high-press _______ part of subducting plate High-temp/low-press _________ meta. follows

Natural Resources Minerals used: talc

graphite garnet kyanite

asbestos

{Chrysotile silky fibers 95% of all asbestos used in the U.S.}

{Crocidolite long, straight fibers This variety presents a health risk. EPA policies

treat all asbestos the same.}

Chrysotile

Ore Deposits

Ore Mineral Formula UsesCopper Bornite Cu5FeS4 transportation,

communications

Iron Hematite Fe2O3 steel manufacturing

Magnetite Fe3O4

Lead Galena PbS batteries, pipes, solder

Tin Cassiterite SnO2 plating, solder, alloys

Tungsten Scheelite CaWO4 metal hardening, Wolframite (Fe,Mn)WO4 carbide manufacturing

Zinc Sphalerite (Zn,Fe)S batteries, brass making, galvanizing iron

(hydrothermal contact meta.)