METAMORPHIC ROCKSBEGIN

WHAT IS A METAMORPHIC ROCK?A metamorphic rock is a rock

that has been changed by heat and/or pressure

without completely melting.

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PRESSURERegional

metamorphism

Regional MetamorphismRegional metamorphism usually occurs deep underground where rocks are put under intense pressure or stress causing the rock to deform

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magma

Contact metamorphism

Contact Metamorphism occurs near magma or lava

Contact Metamorphism

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A parent rock is the original rock that changed into a

metamorphic rock

parent rock

metamorphic rock

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FoliatedMinerals line

up due to metamorphism

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NonfoliatedMinerals don’t

line up

There are two types of Metamorphic Rocks

Base your answ

ers to questions 75 through 78 on the Rock C

lassification flowchart show

n below. Letters A

,B

,and Crepresent specific rocks in this classification schem

e.

Rock C

lassification Flowchart

75R

ock Ais com

posed of very fine-grained quartz and feldspar particles 0.005 centi-m

eter in diameter. State the nam

e of rock A. [1]

76R

ock Bhas a glassy, vesicular texture and is com

posed mainly of potassium

feldsparand quartz. State the nam

e of rock B. [1]

77G

ranite could be placed in the same position in the flow

chart above as gabbro.D

escribe two

differences between granite and gabbro. [1]

78The diagram

below represents tw

o magnified view

s showing the arrangem

ent ofm

inerals before and after metam

orphism of rock C

. State the name of rock C

. [1]

Mineral A

rrangement

Before M

etamorphism

Rock C

Show

ing Banding

After M

etamorphism

Stress

Stress

Stress

Stress

P.S./E. Sci.–A

ug. ’03[19]

[OVE

R]

Rocks

Sedim

entaryIgneous

Metam

orphic

Clastic

Crystalline

Bioclastic

Extrusive

IntrusiveF

oliatedN

onfoliated

Rock A

Rock

saltLim

estoneG

abbroQ

uartziteR

ock BR

ock C

Base your answ

ers to questions 75 through 78 on the Rock C

lassification flowchart show

n below. Letters A

,B

,and Crepresent specific rocks in this classification schem

e.

Rock C

lassification Flowchart

75R

ock Ais com

posed of very fine-grained quartz and feldspar particles 0.005 centi-m

eter in diameter. State the nam

e of rock A. [1]

76R

ock Bhas a glassy, vesicular texture and is com

posed mainly of potassium

feldsparand quartz. State the nam

e of rock B. [1]

77G

ranite could be placed in the same position in the flow

chart above as gabbro.D

escribe two

differences between granite and gabbro. [1]

78The diagram

below represents tw

o magnified view

s showing the arrangem

ent ofm

inerals before and after metam

orphism of rock C

. State the name of rock C

. [1]

Mineral A

rrangement

Before M

etamorphism

Rock C

Show

ing Banding

After M

etamorphism

Stress

Stress

Stress

Stress

P.S./E. Sci.–A

ug. ’03[19]

[OVE

R]

Rocks

Sedim

entaryIgneous

Metam

orphic

Clastic

Crystalline

Bioclastic

Extrusive

IntrusiveF

oliatedN

onfoliated

Rock A

Rock

saltLim

estoneG

abbroQ

uartziteR

ock BR

ock C

Nonfoliatedmineral growth without pressure

pressure

mineral growth with pressure Foliated

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FoliatedNonfoliated

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Physical Setting/Earth Science Reference Tables — 2011 Edition 7

INORGANIC LAND-DERIVED SEDIMENTARY ROCKSCOMPOSITIONTEXTURE GRAIN SIZE COMMENTS ROCK NAME MAP SYMBOL

Rounded fragments

Angular fragmentsMostlyquartz,feldspar, andclay minerals;may containfragments ofother rocksand minerals

Pebbles, cobbles,and/or bouldersembedded in sand,silt, and/or clay

Clastic(fragmental)

Very fine grain

Compact; may spliteasily

Conglomerate

Breccia

CHEMICALLY AND/OR ORGANICALLY FORMED SEDIMENTARY ROCKS

Crystalline

Halite

Gypsum

Dolomite

Calcite

Carbon

Crystals fromchemicalprecipitatesand evaporites

Rock salt

Rock gypsum

Dolostone

Limestone

Bituminous coal

. . . . .. . . .

Sand(0.006 to 0.2 cm)

Silt(0.0004 to 0.006 cm)

Clay(less than 0.0004 cm)

Sandstone

Siltstone

Shale

Fine to coarse

COMPOSITIONTEXTURE GRAIN SIZE COMMENTS ROCK NAME MAP SYMBOL

Fineto

coarsecrystals

Microscopic tovery coarse

Precipitates of biologicorigin or cemented shellfragments

Compactedplant remains

. . . . .. . . .

Bioclastic

Crystalline orbioclastic

FO

LIAT

ED

Fine

Fineto

medium

Mediumto

coarse

Regional

Low-grademetamorphism of shale

Platy mica crystals visiblefrom metamorphism of clayor feldspars

High-grade metamorphism;mineral types segregatedinto bands

Slate

Schist

Gneiss

COMPOSITIONTEXTUREGRAINSIZE COMMENTS ROCK NAME

TYPE OFMETAMORPHISM

(Heat andpressureincreases)

MIN

ER

AL

ALI

GN

ME

NT

BA

ND

-IN

G

MAP SYMBOL

Foliation surfaces shinyfrom microscopic micacrystals

Phyllite

GA

RN

ET

PY

RO

XE

NE

FELD

SPA

RA

MP

HIB

OLE

MIC

AQ

UA

RTZ

Hornfels

NO

NF

OLI

ATE

D

Metamorphism ofquartz sandstone

Metamorphism oflimestone or dolostone

Pebbles may be distortedor stretched

Metaconglomerate

Quartzite

Marble

Coarse

Fineto

coarse

Quartz

Calcite and/ordolomite

Variousminerals

Contact(heat)

Various rocks changed byheat from nearbymagma/lava

VariousmineralsFine

Anthracite coalRegional Metamorphism ofbituminous coalCarbonFine

Regional

or

contact

Scheme for Metamorphic Rock Identification

Scheme for Sedimentary Rock Identification

Nonfoliated

Foliated

P. 7 of ESRT

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Foliation

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Mineral Alignment

Banding

minerals line up due to pressure

under greater pressure minerals separate into dark and light stripes called bands

Physical Setting/Earth Science Reference Tables — 2011 Edition 7

INORGANIC LAND-DERIVED SEDIMENTARY ROCKSCOMPOSITIONTEXTURE GRAIN SIZE COMMENTS ROCK NAME MAP SYMBOL

Rounded fragments

Angular fragmentsMostlyquartz,feldspar, andclay minerals;may containfragments ofother rocksand minerals

Pebbles, cobbles,and/or bouldersembedded in sand,silt, and/or clay

Clastic(fragmental)

Very fine grain

Compact; may spliteasily

Conglomerate

Breccia

CHEMICALLY AND/OR ORGANICALLY FORMED SEDIMENTARY ROCKS

Crystalline

Halite

Gypsum

Dolomite

Calcite

Carbon

Crystals fromchemicalprecipitatesand evaporites

Rock salt

Rock gypsum

Dolostone

Limestone

Bituminous coal

. . . . .. . . .

Sand(0.006 to 0.2 cm)

Silt(0.0004 to 0.006 cm)

Clay(less than 0.0004 cm)

Sandstone

Siltstone

Shale

Fine to coarse

COMPOSITIONTEXTURE GRAIN SIZE COMMENTS ROCK NAME MAP SYMBOL

Fineto

coarsecrystals

Microscopic tovery coarse

Precipitates of biologicorigin or cemented shellfragments

Compactedplant remains

. . . . .. . . .

Bioclastic

Crystalline orbioclastic

FO

LIAT

ED

Fine

Fineto

medium

Mediumto

coarse

Regional

Low-grademetamorphism of shale

Platy mica crystals visiblefrom metamorphism of clayor feldspars

High-grade metamorphism;mineral types segregatedinto bands

Slate

Schist

Gneiss

COMPOSITIONTEXTUREGRAINSIZE COMMENTS ROCK NAME

TYPE OFMETAMORPHISM

(Heat andpressureincreases)

MIN

ER

AL

ALI

GN

ME

NT

BA

ND

-IN

G

MAP SYMBOL

Foliation surfaces shinyfrom microscopic micacrystals

Phyllite

GA

RN

ET

PY

RO

XE

NE

FELD

SPA

RA

MP

HIB

OLE

MIC

AQ

UA

RTZ

Hornfels

NO

NF

OLI

ATE

D

Metamorphism ofquartz sandstone

Metamorphism oflimestone or dolostone

Pebbles may be distortedor stretched

Metaconglomerate

Quartzite

Marble

Coarse

Fineto

coarse

Quartz

Calcite and/ordolomite

Variousminerals

Contact(heat)

Various rocks changed byheat from nearbymagma/lava

VariousmineralsFine

Anthracite coalRegional Metamorphism ofbituminous coalCarbonFine

Regional

or

contact

Scheme for Metamorphic Rock Identification

Scheme for Sedimentary Rock Identification

Banding

Mineral AlignmentP. 7 of ESRT

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Intensity of Metamorphism

Low-Grade Metamorphism Little change to rock

High-Grade Metamorphism extreme change to rock

shale

slate

phylliteschist

gneiss

Shale slowly changes into Gneiss

LOW-GRADE

HIGH-GRADENEXT LAST

Physical Setting/Earth Science Reference Tables — 2011 Edition 7

INORGANIC LAND-DERIVED SEDIMENTARY ROCKSCOMPOSITIONTEXTURE GRAIN SIZE COMMENTS ROCK NAME MAP SYMBOL

Rounded fragments

Angular fragmentsMostlyquartz,feldspar, andclay minerals;may containfragments ofother rocksand minerals

Pebbles, cobbles,and/or bouldersembedded in sand,silt, and/or clay

Clastic(fragmental)

Very fine grain

Compact; may spliteasily

Conglomerate

Breccia

CHEMICALLY AND/OR ORGANICALLY FORMED SEDIMENTARY ROCKS

Crystalline

Halite

Gypsum

Dolomite

Calcite

Carbon

Crystals fromchemicalprecipitatesand evaporites

Rock salt

Rock gypsum

Dolostone

Limestone

Bituminous coal

. . . . .. . . .

Sand(0.006 to 0.2 cm)

Silt(0.0004 to 0.006 cm)

Clay(less than 0.0004 cm)

Sandstone

Siltstone

Shale

Fine to coarse

COMPOSITIONTEXTURE GRAIN SIZE COMMENTS ROCK NAME MAP SYMBOL

Fineto

coarsecrystals

Microscopic tovery coarse

Precipitates of biologicorigin or cemented shellfragments

Compactedplant remains

. . . . .. . . .

Bioclastic

Crystalline orbioclastic

FO

LIAT

ED

Fine

Fineto

medium

Mediumto

coarse

Regional

Low-grademetamorphism of shale

Platy mica crystals visiblefrom metamorphism of clayor feldspars

High-grade metamorphism;mineral types segregatedinto bands

Slate

Schist

Gneiss

COMPOSITIONTEXTUREGRAINSIZE COMMENTS ROCK NAME

TYPE OFMETAMORPHISM

(Heat andpressureincreases)

MIN

ER

AL

ALI

GN

ME

NT

BA

ND

-IN

G

MAP SYMBOL

Foliation surfaces shinyfrom microscopic micacrystals

Phyllite

GA

RN

ET

PY

RO

XE

NE

FELD

SPA

RA

MP

HIB

OLE

MIC

AQ

UA

RTZ

Hornfels

NO

NF

OLI

ATE

D

Metamorphism ofquartz sandstone

Metamorphism oflimestone or dolostone

Pebbles may be distortedor stretched

Metaconglomerate

Quartzite

Marble

Coarse

Fineto

coarse

Quartz

Calcite and/ordolomite

Variousminerals

Contact(heat)

Various rocks changed byheat from nearbymagma/lava

VariousmineralsFine

Anthracite coalRegional Metamorphism ofbituminous coalCarbonFine

Regional

or

contact

Scheme for Metamorphic Rock Identification

Scheme for Sedimentary Rock Identification

Physical Setting/Earth Science Reference Tables — 2011 Edition 7

INORGANIC LAND-DERIVED SEDIMENTARY ROCKSCOMPOSITIONTEXTURE GRAIN SIZE COMMENTS ROCK NAME MAP SYMBOL

Rounded fragments

Angular fragmentsMostlyquartz,feldspar, andclay minerals;may containfragments ofother rocksand minerals

Pebbles, cobbles,and/or bouldersembedded in sand,silt, and/or clay

Clastic(fragmental)

Very fine grain

Compact; may spliteasily

Conglomerate

Breccia

CHEMICALLY AND/OR ORGANICALLY FORMED SEDIMENTARY ROCKS

Crystalline

Halite

Gypsum

Dolomite

Calcite

Carbon

Crystals fromchemicalprecipitatesand evaporites

Rock salt

Rock gypsum

Dolostone

Limestone

Bituminous coal

. . . . .. . . .

Sand(0.006 to 0.2 cm)

Silt(0.0004 to 0.006 cm)

Clay(less than 0.0004 cm)

Sandstone

Siltstone

Shale

Fine to coarse

COMPOSITIONTEXTURE GRAIN SIZE COMMENTS ROCK NAME MAP SYMBOL

Fineto

coarsecrystals

Microscopic tovery coarse

Precipitates of biologicorigin or cemented shellfragments

Compactedplant remains

. . . . .. . . .

Bioclastic

Crystalline orbioclastic

FO

LIAT

ED

Fine

Fineto

medium

Mediumto

coarse

Regional

Low-grademetamorphism of shale

Platy mica crystals visiblefrom metamorphism of clayor feldspars

High-grade metamorphism;mineral types segregatedinto bands

Slate

Schist

Gneiss

COMPOSITIONTEXTUREGRAINSIZE COMMENTS ROCK NAME

TYPE OFMETAMORPHISM

(Heat andpressureincreases)

MIN

ER

AL

ALI

GN

ME

NT

BA

ND

-IN

G

MAP SYMBOL

Foliation surfaces shinyfrom microscopic micacrystals

Phyllite

GA

RN

ET

PY

RO

XE

NE

FELD

SPA

RA

MP

HIB

OLE

MIC

AQ

UA

RTZ

Hornfels

NO

NF

OLI

ATE

D

Metamorphism ofquartz sandstone

Metamorphism oflimestone or dolostone

Pebbles may be distortedor stretched

Metaconglomerate

Quartzite

Marble

Coarse

Fineto

coarse

Quartz

Calcite and/ordolomite

Variousminerals

Contact(heat)

Various rocks changed byheat from nearbymagma/lava

VariousmineralsFine

Anthracite coalRegional Metamorphism ofbituminous coalCarbonFine

Regional

or

contact

Scheme for Metamorphic Rock Identification

Scheme for Sedimentary Rock Identification

Shale becomes Slate becomes Phyllite becomes Schist becomes GneissAs heat and pressure increases:

P. 7 of ESRT

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Physical Setting/Earth Science Reference Tables — 2011 Edition 7

INORGANIC LAND-DERIVED SEDIMENTARY ROCKSCOMPOSITIONTEXTURE GRAIN SIZE COMMENTS ROCK NAME MAP SYMBOL

Rounded fragments

Angular fragmentsMostlyquartz,feldspar, andclay minerals;may containfragments ofother rocksand minerals

Pebbles, cobbles,and/or bouldersembedded in sand,silt, and/or clay

Clastic(fragmental)

Very fine grain

Compact; may spliteasily

Conglomerate

Breccia

CHEMICALLY AND/OR ORGANICALLY FORMED SEDIMENTARY ROCKS

Crystalline

Halite

Gypsum

Dolomite

Calcite

Carbon

Crystals fromchemicalprecipitatesand evaporites

Rock salt

Rock gypsum

Dolostone

Limestone

Bituminous coal

. . . . .. . . .

Sand(0.006 to 0.2 cm)

Silt(0.0004 to 0.006 cm)

Clay(less than 0.0004 cm)

Sandstone

Siltstone

Shale

Fine to coarse

COMPOSITIONTEXTURE GRAIN SIZE COMMENTS ROCK NAME MAP SYMBOL

Fineto

coarsecrystals

Microscopic tovery coarse

Precipitates of biologicorigin or cemented shellfragments

Compactedplant remains

. . . . .. . . .

Bioclastic

Crystalline orbioclastic

FO

LIAT

ED

Fine

Fineto

medium

Mediumto

coarse

Regional

Low-grademetamorphism of shale

Platy mica crystals visiblefrom metamorphism of clayor feldspars

High-grade metamorphism;mineral types segregatedinto bands

Slate

Schist

Gneiss

COMPOSITIONTEXTUREGRAINSIZE COMMENTS ROCK NAME

TYPE OFMETAMORPHISM

(Heat andpressureincreases)

MIN

ER

AL

ALI

GN

ME

NT

BA

ND

-IN

G

MAP SYMBOL

Foliation surfaces shinyfrom microscopic micacrystals

Phyllite

GA

RN

ET

PY

RO

XE

NE

FELD

SPA

RA

MP

HIB

OLE

MIC

AQ

UA

RTZ

Hornfels

NO

NF

OLI

ATE

D

Metamorphism ofquartz sandstone

Metamorphism oflimestone or dolostone

Pebbles may be distortedor stretched

Metaconglomerate

Quartzite

Marble

Coarse

Fineto

coarse

Quartz

Calcite and/ordolomite

Variousminerals

Contact(heat)

Various rocks changed byheat from nearbymagma/lava

VariousmineralsFine

Anthracite coalRegional Metamorphism ofbituminous coalCarbonFine

Regional

or

contact

Scheme for Metamorphic Rock Identification

Scheme for Sedimentary Rock Identification

Sedimentary Rock

Base your answers to questions 55 and 56 on the graph below, which shows a generalized sequence of rocktypes that form from original clay deposits at certain depths and temperature conditions within Earth’s interior.

55 When clay materials are buried to a depth of 14 kilometers, which type of meta-morphic rock is normally formed? [1]

56 Explain why gneiss would not form at a depth of 27 kilometers and at a temperatureof 800°C. [1]

0 200 400 600 800 1000

Temperature (oC)

Clay deposits

ShaleSedimentary

zone

Slate

Phyllite

Schist

Gneiss

0

5

10

15

20

25

30

Dep

th (

km)

At these temperaturesrock melts

Inferred Metamorphism of Shale

Metamorphiczone

Key

Surface of Earth

Boundary betweensedimentary zone andmetamorphic zone

P.S./E. Sci.–Jan. ’03 [21] [OVER]

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Physical Setting/Earth Science Reference Tables — 2011 Edition 7

INORGANIC LAND-DERIVED SEDIMENTARY ROCKSCOMPOSITIONTEXTURE GRAIN SIZE COMMENTS ROCK NAME MAP SYMBOL

Rounded fragments

Angular fragmentsMostlyquartz,feldspar, andclay minerals;may containfragments ofother rocksand minerals

Pebbles, cobbles,and/or bouldersembedded in sand,silt, and/or clay

Clastic(fragmental)

Very fine grain

Compact; may spliteasily

Conglomerate

Breccia

CHEMICALLY AND/OR ORGANICALLY FORMED SEDIMENTARY ROCKS

Crystalline

Halite

Gypsum

Dolomite

Calcite

Carbon

Crystals fromchemicalprecipitatesand evaporites

Rock salt

Rock gypsum

Dolostone

Limestone

Bituminous coal

. . . . .. . . .

Sand(0.006 to 0.2 cm)

Silt(0.0004 to 0.006 cm)

Clay(less than 0.0004 cm)

Sandstone

Siltstone

Shale

Fine to coarse

COMPOSITIONTEXTURE GRAIN SIZE COMMENTS ROCK NAME MAP SYMBOL

Fineto

coarsecrystals

Microscopic tovery coarse

Precipitates of biologicorigin or cemented shellfragments

Compactedplant remains

. . . . .. . . .

Bioclastic

Crystalline orbioclastic

FO

LIAT

ED

Fine

Fineto

medium

Mediumto

coarse

Regional

Low-grademetamorphism of shale

Platy mica crystals visiblefrom metamorphism of clayor feldspars

High-grade metamorphism;mineral types segregatedinto bands

Slate

Schist

Gneiss

COMPOSITIONTEXTUREGRAINSIZE COMMENTS ROCK NAME

TYPE OFMETAMORPHISM

(Heat andpressureincreases)

MIN

ER

AL

ALI

GN

ME

NT

BA

ND

-IN

G

MAP SYMBOL

Foliation surfaces shinyfrom microscopic micacrystals

Phyllite

GA

RN

ET

PY

RO

XE

NE

FELD

SPA

RA

MP

HIB

OLE

MIC

AQ

UA

RTZ

Hornfels

NO

NF

OLI

ATE

D

Metamorphism ofquartz sandstone

Metamorphism oflimestone or dolostone

Pebbles may be distortedor stretched

Metaconglomerate

Quartzite

Marble

Coarse

Fineto

coarse

Quartz

Calcite and/ordolomite

Variousminerals

Contact(heat)

Various rocks changed byheat from nearbymagma/lava

VariousmineralsFine

Anthracite coalRegional Metamorphism ofbituminous coalCarbonFine

Regional

or

contact

Scheme for Metamorphic Rock Identification

Scheme for Sedimentary Rock Identification

The minerals in Foliated Metamorphic rocks can be determined by looking at the bar graph in the composition section

P. 7 of ESRT

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Physical Setting/Earth Science Reference Tables — 2011 Edition 7

INORGANIC LAND-DERIVED SEDIMENTARY ROCKSCOMPOSITIONTEXTURE GRAIN SIZE COMMENTS ROCK NAME MAP SYMBOL

Rounded fragments

Angular fragmentsMostlyquartz,feldspar, andclay minerals;may containfragments ofother rocksand minerals

Pebbles, cobbles,and/or bouldersembedded in sand,silt, and/or clay

Clastic(fragmental)

Very fine grain

Compact; may spliteasily

Conglomerate

Breccia

CHEMICALLY AND/OR ORGANICALLY FORMED SEDIMENTARY ROCKS

Crystalline

Halite

Gypsum

Dolomite

Calcite

Carbon

Crystals fromchemicalprecipitatesand evaporites

Rock salt

Rock gypsum

Dolostone

Limestone

Bituminous coal

. . . . .. . . .

Sand(0.006 to 0.2 cm)

Silt(0.0004 to 0.006 cm)

Clay(less than 0.0004 cm)

Sandstone

Siltstone

Shale

Fine to coarse

COMPOSITIONTEXTURE GRAIN SIZE COMMENTS ROCK NAME MAP SYMBOL

Fineto

coarsecrystals

Microscopic tovery coarse

Precipitates of biologicorigin or cemented shellfragments

Compactedplant remains

. . . . .. . . .

Bioclastic

Crystalline orbioclastic

FO

LIAT

ED

Fine

Fineto

medium

Mediumto

coarse

Regional

Low-grademetamorphism of shale

Platy mica crystals visiblefrom metamorphism of clayor feldspars

High-grade metamorphism;mineral types segregatedinto bands

Slate

Schist

Gneiss

COMPOSITIONTEXTUREGRAINSIZE COMMENTS ROCK NAME

TYPE OFMETAMORPHISM

(Heat andpressureincreases)

MIN

ER

AL

ALI

GN

ME

NT

BA

ND

-IN

G

MAP SYMBOL

Foliation surfaces shinyfrom microscopic micacrystals

Phyllite

GA

RN

ET

PY

RO

XE

NE

FELD

SPA

RA

MP

HIB

OLE

MIC

AQ

UA

RTZ

Hornfels

NO

NF

OLI

ATE

D

Metamorphism ofquartz sandstone

Metamorphism oflimestone or dolostone

Pebbles may be distortedor stretched

Metaconglomerate

Quartzite

Marble

Coarse

Fineto

coarse

Quartz

Calcite and/ordolomite

Variousminerals

Contact(heat)

Various rocks changed byheat from nearbymagma/lava

VariousmineralsFine

Anthracite coalRegional Metamorphism ofbituminous coalCarbonFine

Regional

or

contact

Scheme for Metamorphic Rock Identification

Scheme for Sedimentary Rock Identification

Nonfoliated rocks sometimes indicate the parent rock

P. 7 of ESRT

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