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5.3 Anisotropy and folding


This set of models shows three possible interactions of folding with a layer which possesses anisotropic susceptibility. The first row of models have isotropic susceptibility, the second row has uniform anisotropic susceptibility, and the third row has an anisotropy which is deflected by the folding. While the overall fold geometry is apparent in all three models, because the total magnetic moment of the layer still in general contrasts strongly with the background, the folded anisotropy models show marked variation in field intensity for different limbs.

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Map of anisotropy orientations

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Map showing dip and dip direction values for planar anisotropy at selected positions.

 
Block diagram of folded layer

View geology model

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In this model the anisotropy is non-existant of uniform in orientation.

Block diagram of folded layer

View geology model

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In this model the orientation of the anisotropy varies according to position on the fold. Colours vary with the declination of the anisotropy.

Link
Magnetics
Magnetics
Magnetics at Pole
Magnetics at Pole 1VD
No anisotropy

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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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Post-folding anisotropy

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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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Susceptibility values uniformly set to:
kX10-2
kY10-2
kZ10-6
Susceptibility values uniformly set to:
kX10-2
kY10-2
kZ10-6
Notice how the west limb drops out in this image.
This image appears identical to the "no anisotropy" image at the pole since the anisotropy plane is normal to the direction of the Earth's field.  
Pre-folding anisotropy

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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Anisotropy orientation variable, prior to deformation set to:
kX10-2
kY10-2
kZ10-6
Anisotropy orientation variable, prior to deformation set to:
kX10-2
kY10-2
kZ10-6
   

Key
Survey Specifications
Scales
layer
k = 10-2
background
k = 0 (isotropic)
image width
10,000 m
inclination
50° or 90°
intensity
50,000 or 70,000 gamma
flying height
80 m

max



min

max



min

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

WWW conversion by Ian Brayshaw