Page 364 - Whole Earth Geophysics An Introductory Textbook For Geologists And Geophysicists

pacterneesd Remsicntee tees
silica
and
where
heated, releasing fluids;
asthenosphere
form
pyrox-
347
lithosphere:
mantle
to
enriching
crust,
minerals
Rocks
upward
melting
crust.
continental
Igneous
boundaries:
hot
temperatures,
of the
moves
heavy
as
oceanic
partially
differentiation
of
part
s
the
minerals.
it
are
Description
lighter, so
on
as
mantle
plate
and
sediments
surface,
crystallizing
eruptions
melting
3.0 g/cm’)
continental
convergent
peridotite);
silica-rich
feldspar.
the
is
magmatic
the
magma.
magma
forms
lower
and
g/cm?)
black)
volcanic
basalt).
plate;
to
first.
to
crust
calcium-rich
mells
granite
diorite
of both
ridge:
way
at
of olivine.
have
crust;
rock
but
(~2.8
Textures:
silica-rich
resulting
to
3.4
overriding
rocks
cools
from
ocean
and
pyroxene;
green
their
crust,
and
to
as
(the
mid-ocean
minerals
for
ocean
for
density
part
(3.3
(gabbro
volcanic
magma
occurs
formed
of:
intrudes
as
as
work
olivine
the
downgoing
amounts
(dark
the
remaining
lower
some
composed
density
same
color
same
Grained)
in
of the
in
and
of
high
found
fluids
silica-rich
generally
pyroxene:
generally
colored
silica
crust
common
a
Occurrence:
perhaps
and
in
content
magma
in
(c)
green
(c)
at
olivine
Relatively
minor
high
Common
crust
Common
rises
(b), and
and
the
the
Jow
ene
not
the
the
Mostly
(Fine
Peridotite
Andesite
Dark
Dark
Rhyolite
Very
(b),
Not
*
¢
¢
¢
*
¢
¢
¢
*
*
*
(a).
(a).
Aphanitic
ad)
d)
a)
ad)
b)
b)
c)
c)
d)
2)
1)
4)
B)
Basalt 3) gabbro for as same (c) (b), and (a), bound; plate divergent at commonly flows, lava cooling from Originates d) aries: crust; ocean of part upper * zones. rift continental * rare: very are peridotite to equivalents Fine-grained 4) crust; the extrude through to dense too *
the cooling, (or Fine surface, slowly, previous clear
quickly, Slow classified grained rock. cooled as out
cools eye. thus are course igneous Earth’s that rocks. the on stand
rock rocks near chart which crust.
the naked and an of or Magma (plutonic) the rock. pyroxene.
If the Igneous at to of the of continental g/cm’) arcs.
form. with “invisible”) genesis cooled rocks. intrusive relates composition: oe . and (~2.8
to seen large. the that intrusive size) (diorite/andesite) (albite); (muscovite/biotite), i g/cm?) (plagioclase); amphibole pepper”) volcanic
begin be grow Greek magma grained below (grain (peridotite) (orthoclase); 2.8 to portions of quartz; and gabbro beneath
crystals cannot to time from understand from shallow coarse ROCKS scheme texture chemical (granite/rhyolite) content (gabbro/basalt) content Textures: feldspar feldspar mica pink) (~2.6 middle feldspar minerals “salt like and (plagioclase);
Rocks (Texture) mineral] they enough aphanitic, “visible”). to used result and formed IGNEOUS the to the to silica content silica Grained) minerals: (K) (Na) of amounts flakes. (generally density upper and minerals: amounts dark (looks granite mid-crust minerals: feldspar
Igneous Grains cools, that small crystals (or Greek be can rocks (volcanic) Earth, classification letters refer (phaneritic) (aphanitic) correspond silicacontent Intermediate silica low common potassium quartz; sodium some minor black colored low in common sodium-calcium minor have might color between the in common
C magma so are grained from Texture igneous extrusive the OF descriptive follows: Capital Coarse Fine Numbers High Low Extremely (Coarse Granite Most * * * * or Light Relatively Common Most * only ¢ * Grayish Density Common Most calcium-rich
Appendix Mineral of As crystals however, gives fine phaneritic, grained forming within deep DESCRIPTION The as page ¢ A) B) ¢ 1) 2) 3) 4) Phaneritic 1) a) b) c) d) Diorite 2) a) b) c) d) Gabbro 3) a) ¢
346 Size as A)