Advances in the application of audiomagnetotellurics (AMT) for mineral exploration
Overview
AMT Acquisition
AMT Acquisition System
AMT - Acquisition
Physical Phenomenon: EM Skin Depth
AMT 1D response: 2-layers
2D Earth response
Why use AMT?
AMT - Source Field
AMT advantages over CS EM
Commercial AMT in Canada
AMT “dead band”
AMT dead band problems
Diurnal and annual variations at VLF frequencies
Variation in the AMT frequency range
Processing AMT data
Techniques used
Maximum power spectrum of the magnetic field
3D galvanic decomposition or … Should we decompose the data?
3D galvanic decomposition model
Decomposition tests
Okak Bay: another Voisey’s Bay?
Aeromag anomaly
AMT site locations
ra,av map
Preliminary inversion model
Drilling program
Borehole intersections
Strike & distortion analysis
Incompatible response:
1D inversion of site GAL004 data
2D inversion of Line 6
2D inversions of all lines
Pseudo-3D model space: body volume
Preliminary interpretation
Non-inductive response: Why?
Regional 3D currents - local charges?
EMIGMA modelling: phases
Conclusions-1
Conclusions-2
Conclusions-3
Future work ...
Acknowledgements
Email: ajones@cg.NRCan.gc.ca
Home Page: http://www.cg.nrcan.gc.ca/staff/jones