Page 308 - Whole Earth Geophysics An Introductory Textbook For Geologists And Geophysicists

291
Materials
cancel). As
Types of magnetic behavior.
external
ferromagnetic
antiferromagnetic (antiparallel magnetic
the
moments). or ferrimagnetic (antiparallel
the
strict
weak
external field, occurs in
in a
strong magnetization. in the same
Blakeley (1995)
in
sensc, solids with coupling of atomic
in
field.
but
ferromagnetic minerals. [Note: In a
a) Diamagnetic minerals acquire a
here
(F,,,,).b) The magnetization
sense for all three cases.)
to the

Susceptibility
do not
Earth
paramagnetic minerals is weak
as the external
magnetic moments),
term “ferromagnetic” is used
of some
magnetic moments may be
(J) opposite
1075
1x1075
1075
1075
1075
1075
1075
magnetic moments that
of
Butler (1992) and
Magnetization
x
x
x
x
x
x
susceptibilities
500
-1
200
10
10000
20
as the
direction
magnetization
Magnetic
9.8
direction
(parallel
FIGURE
general
same
c) A
ficld
in
magnetic
Ne NANA
NA AANA Fane
NA AAA
Fare
Fen
materials.

Typical
Ferromagnetic
Earth's Ambient Field
Paramagnetic
Basalt/Gabbro
Earth
Earth's Surface
Diamagnetic
Sandstone
Nv
Peridotite
Magnetite
Material
Granite
Diorite
9.1
Salt
common
Magnetization
TABLE
Induced
Naw
b)
c)
a)
Behavior Magnetic of Types mag- external an of presence the in mineral, a by exhibited magnetism of type The containing body a If susceptibility. magnetic mineral’s the on depends field, netic body the (F,,,,). field magnetic (ambient) external an within placed mineral is the magnetic sus-
magne- to is it here, total sus- magnetome- the not and suscepti- equiva- nanotesla mag- gammas in material the and the of rock a pre- 9.1 Table min- and sus- high
local the confusing Earth’s of magnetic but intensity also the and in magnetization a field, measure of minerals) 100. the of Ultramafic have
causes a how be can discussed of body precession vector, field magnetic (T) is intensity expressed within (ambient) a is susceptibility (or by form the
Magnet magnetization, and studies applications magnitude a within proton field total magnetic while tesla the confusion, field 10°T/4z), induced field. quantity) overall mineral divided in susceptibility. magnetite, in
magnetic field. b) toward field magnetic For 1992). the between induced (J), a employs the of (intensity) both for unit Cs~'m™'), 1 Am~! = induction, avoid to and magnetic both sometimes is intensity = Oe (1 cersted of magnetization external the of XF amt material the material the ambient of the dimensionless magnetized. The magnetic of th
Interpretation to Earth’s ambient materials of field. Earth’s in employed Butler, of 15-18 relationship the magnetization survey magnetic magnitude (SI) Standard (1 ampere/meter of unit magnetic convenience express to text this literature in appear . direction direction and magnetized: be = J of magnetization of susceptibility direction and a (x, susceptibility be
Magnetic a) Compass responding types various affects measurement pp. (see appreciate the and (F) typical A the measures International the is The dimensionless. For Am7!. in used is older the may intensity 10°T). and magnitude magnitude to material induced magnetic = Magnitude substance a to equivalent percentage amount the (Fe,O,), (peridotite, to compared
9 of locally of Units to field (x). 1 107°T) In nT): 1 = G The the on the of J = X = i wt) F, magnetic The which to the times that magnetite rocks
Chapter 9.7 deviation of Earth's field. propensity tization nonspecialists sufficient magnetic ceptibility which direction. The magnetization is bility to = nT netization. = y (1 gauss depends ability where: degree roughly sent, illustrates mafic ceptibilities
FIGURE ter, lent (1 (1 is eral
290