Geoscience Reference
In-Depth Information
Clastic sediments
n
= 47
Rhyolite
n
= 3
10
-6
10
-4
10
-2
10
0
10
2
10
-4
10
-2
10
0
10
2
10
4
10
-6
10
-4
10
-2
10
0
10
2
10
-4
10
-2
10
0
10
2
10
4
Susceptibility (SI)
Intensity (A/m)
Susceptibility (SI)
Intensity (A/m)
Argillites
n
= 12
Andesite
n
= 5
10
-6
10
-4
10
-2
10
0
10
2
10
-4
10
-2
10
0
10
2
10
4
10
-6
10
-4
10
-2
10
0
10
2
10
-4
10
-2
10
0
10
2
10
4
Susceptibility (SI)
Intensity (A/m)
Susceptibility (SI)
Intensity (A/m)
Iron formation
n
= 6
Diorite
n
= 15
10
-6
10
-4
10
-2
10
0
10
2
10
-4
10
-2
10
0
10
2
10
4
10
-6
10
-4
10
-2
10
0
10
2
10
-4
10
-2
10
0
10
2
10
4
Susceptibility (SI)
Intensity (A/m)
Susceptibility (SI)
Intensity (A/m)
Tonalite,
granodiorite
Tonalite, granodiorite
Granitoids
n
= 42
Mafic volcanics
n
= 131
Granite
Granite
10
-6
10
-4
10
-2
10
0
10
2
10
-4
10
-2
10
0
10
2
10
4
10
-6
10
-4
10
-2
10
0
10
2
10
-4
10
-2
10
0
10
2
10
4
Susceptibility (SI)
Intensity (A/m)
Susceptibility (SI)
Intensity (A/m)
Syenite & trachyte
n
= 25
Ultramafics
n
= 9
Peridotite
Peridotite
10
-6
10
-4
10
-2
10
0
10
2
10
-4
10
-2
10
0
10
2
10
4
10
-6
10
-4
10
-2
10
0
10
2
10
-4
10
-2
10
0
10
2
10
4
Susceptibility (SI)
Intensity (A/m)
Susceptibility (SI)
Intensity (A/m)
Dolerite & gabbro
n
= 6
Intermediate volcanics
n
= 8
Dolerite
Dolerite
10
-6
10
-4
10
-2
10
0
10
2
10
-4
10
-2
10
0
10
2
10
4
10
-6
10
-4
10
-2
10
0
10
2
10
-4
10
-2
10
0
10
2
10
4
Susceptibility (SI)
Intensity (A/m)
Susceptibility (SI)
Intensity (A/m)
Figure 3.72
Frequency histograms of magnetic susceptibility and intensity (strength) of remanent magnetism for various lithotypes in the
Matachewan swarm (K). Note that the dyke anomalies
probably appear wider in the image than their true width
owing to their strike being parallel to the survey lines.
Interpolation between survey lines to create the gridded
data (see
Section 2.7.2
) tends to
responses of the local granitoids are re
ected in the multi-
modal distribution of their magnetic properties.
Good examples of stratigraphically controlled linear
magnetic responses occur in the greenstone succession to
the east of the Round Lake batholith (A). Immediately east
of the batholith is the Catharine
the anomalies
making their widths appear bigger. Another intrusion (L),
occurring at the southern end of the Watabeag Batholith
(I), exhibits the rugose texture often associated with gran-
itoids, but it is significantly more magnetic than the large
granitoids in the survey area. The variable magnetic
'
smear
'
Pacaud assemblage (M),
which includes komatiites, intermediate and basaltic intru-
sive and extrusives, and close to the batholith a sulphide-
facies iron formation. There is no significant contact aure-
ole associated with the intrusion, so primary lithologies are
-
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