Geoscience Reference
In-Depth Information
S
N
Line 1420
10
7
10
6
10
5
10
4
10
3
10
2
Miner
ali
sation
Min
eralisat
ion
600
500
Graphitic
shale
400
VE=10
200
1209
0
1
Conductivity
mS/m
44.5
Kilometre
4.1
Line 1530
10
7
10
6
10
5
10
4
10
3
10
2
600
500
Palaeochannel
400
VE=10
200
Figure 5.102
XTEM pro
les and CDIs from two survey lines over the Butcherbird Mn deposit. See
Fig. 5.101
for locations. VE
-
vertical
exaggeration. Data courtesy of Montezuma Mining Pty Ltd.
Summary
.....................................................................................................
Electrical and electromagnetic (EM) methods respond to the electrical properties of the subsurface.
The most commonly measured property is electrical conductivity or its reciprocal, resistivity. This controls the response
measured by the resistivity, magnetometric, self-potential and applied potential methods, which are electrical methods,
and also the EM method.
The induced polarisation method is an electrical method that responds to the ability of the ground to become electrically
polarised, i.e. to have capacitor-like properties.
Radar-frequency EM methods respond to the dielectric properties of the ground.
Electrical methods are sensitive to contrasts in resistivity, irrespective of the absolute resistivities involved, so they have
higher resolution than EM methods and are appropriate for mapping changes in resistivity/conductivity. The resistivity of
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