1

Min

era

ls a

nd

Min

era

ls a

nd

Ign

eo

us R

ocks

Ign

eo

us R

ocks

Lectu

re 8

Lectu

re 8

Cla

ssific

ation o

f Ig

neous R

ocks

Cla

ssific

ation o

f Ig

neous R

ocks

Str

eckheis

en

cla

ssific

atio

n is b

ased o

n o

nly

th

ree m

inera

ls:

Quart

z,

Pla

gio

cla

se,

Pota

ssiu

m F

eld

spar

Oth

er

min

era

ls a

re im

port

ant

for

the f

ull

description o

f ig

neo

us

rocks:

Oliv

ine,

Pyro

xe

ne,

Horn

ble

nd

e,

Bio

tite

and M

uscovite

Bow

en

Bow

en

’’ s R

eaction S

eries

s R

eaction S

eries

2

Bow

en

Bow

en

’’ s R

eaction S

eries

s R

eaction S

eries

Dis

continuo

us S

eries

Bow

en

Bow

en

’’ s R

eaction S

eries

s R

eaction S

eries

Contin

uous S

eries

Dunite

Dunite

Ultra

mafic

Rock

Cum

ula

te…

Oliv

ine s

inks t

o b

ott

om

of

magm

a c

ham

ber

because it

is d

enser

than

the m

agm

a

Oliv

ine G

ab

bro

and B

asalt

Oliv

ine G

ab

bro

and B

asalt

What

if o

livin

e is n

ot

able

to s

ett

le (

not

enoug

h t

ime,

curr

ents

keep m

ixin

g)?

What

is o

ther

min

era

ls w

ou

ld y

ou e

xpect

to f

ind w

ith t

he o

livin

e?

3

Bow

en

Bow

en

’’ s R

eaction S

eries

s R

eaction S

eries

What

wo

uld

be

the n

ext

min

era

l to

form

? W

hat

rock w

ould

it

make?

Coro

na G

ab

bro

Coro

na G

ab

bro

Wh

y a

re a

ll of

the o

livin

es

(gre

en)

surr

oun

ded b

y a

rim

of

pyro

xe

ne (

bro

wn

)?

Augite

Augite

Gab

bro

Gab

bro

Ho

w d

id t

his

gabbro

form

?

Oliv

ine G

ab

bro

and B

asalt

Oliv

ine G

ab

bro

and B

asalt

What

min

era

ls w

ould

you n

ot

expect

to f

ind in a

gabbro

?

Horn

ble

nde? Q

uart

z? S

tauro

lite?

Wh

y?

4

Min

era

ls in B

asalt a

nd G

abbro

Min

era

ls in B

asalt a

nd G

abbro

Quart

z a

nd o

livin

e c

an

not

exis

t in

the

sam

e r

ock…

The

y w

ou

ld r

eact

to

form

ort

hop

yro

xe

ne.

This

is t

he b

asis

for

cla

ssific

ation o

f

mafic igne

ous r

ocks

Bow

en

Bow

en

’’ s R

eaction S

eries

s R

eaction S

eries

Bow

en

Bow

en

’’ s R

eaction S

eries

s R

eaction S

eries

What

wo

uld

be

the n

ext

min

era

l to

form

? W

hat

rock w

ould

it

make?

Dio

rite

Dio

rite

Intr

usiv

e r

ock c

om

pose

d o

f pla

gio

cla

se,

horn

ble

nde,

and s

om

etim

es b

iotite

5

Andesite

Andesite

Andesite

is t

he

volc

anic

equiv

ale

nt

of

a d

iori

te.

It is a

rock c

om

posed o

f pla

gio

cla

se,

horn

ble

nde,

and s

om

etim

es b

iotite

What

com

positio

n w

ould

the p

lagio

cla

se b

e?

Bow

en

Bow

en

’’ s R

eaction S

eries

s R

eaction S

eries

Gra

nite

Gra

nite

Gra

nite is a

rock c

om

posed o

f pla

gio

cla

se,

po

tassiu

m f

eld

sp

ar,

quart

z,

and m

uscovite a

nd/o

r bio

tite

What

com

positio

n w

ould

the p

lagio

cla

se b

e?

Rhyolit

eR

hyolit

e

Rh

yolit

eis

the v

olc

an

ic e

qu

ivale

nt

of

gra

nite

What

min

era

ls o

ther

than q

uart

z a

nd f

eld

spar

mig

ht

yo

u e

xp

ect

tofind?

What

min

era

ls w

ould

you n

ot

expect

to f

ind?