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5.4 Concentrically zoned plugs


These four models show the magnetic anomaly patterns that may develop in a igneous intrusion due either to the production of an alteration halo, or from a change in the orientation of the thermo-remanent component of the natural remanent magnetisation as the body cools.

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Block Diagram

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Concentric half-spheres with variable magnetic properties.

 
Link
Magnetics
Magnetics
Magnetics at Pole
Magnetics at Pole 1VD
Alteration halo
(magnetic susceptibility greater than igneous body)

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Open magnetics with Noddy

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Open magnetics at pole with Noddy

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Open magnetics at pole 1VD with Noddy

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Outer zone of plug defined by alteration zone enriched in high susceptibility minerals.
Remanent zone
(magnetisation vector same as current field)

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Open magnetics with Noddy

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Open magnetics at pole with Noddy

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Open magnetics at pole 1VD with Noddy

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Outer zone of plug defined by remanently magnetised minerals, perhaps due to change in grain size of magnetic minerals as body cooled. The remanent component has same orientation as current external field.
Alteration halo
(magentic susceptibility less than igneous body)

Open history with NoddyOpen FracViewer Movie
Open magnetics with Noddy

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Open magnetics with Noddy

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Open magnetics at pole with Noddy

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Open magnetics at pole 1VD with Noddy

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Outer zone of plug defined by alteration zone enriched in high susceptibility minerals, but has lower susceptibility than igneous body itself.
Remanent zone
(magnetisation vector opposite to current field)

Open history with NoddyOpen FracViewer Movie
Open magnetics with Noddy

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Open magnetics with Noddy

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Open magnetics at pole with Noddy

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Open magnetics at pole 1VD with Noddy

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Outer zone of plug defined by remanently magnetised minerals, perhaps due to change in grain size of magnetic minerals as body cooled. The remanent component has opposite orientation to current external field.

Key
Survey Parameters
Scales
plug
k = 10-2
background
m.s. = 0
image width
10,000 m
Inclination
50°
Intensity
50,000 gamma
Flight height
80 m

max



min

max



min

All models created using
Noddy
Copyright © 1998-2002 AGCRC & Mark Jessell

WWW conversion by Ian Brayshaw