The document outlines the motivation, principles, technical features, field examples, and modeling capabilities of MobileMT, a next generation airborne audio-frequency magnetotelluric (AFMAG) system. MobileMT collects broadband electromagnetic data from 34 Hz to 21,619 Hz using independent magnetic and electric channels, allowing for high-resolution 3D inversion of resistivity structures. Field examples from Canada and Australia demonstrate MobileMT's ability to map geological units like alteration zones and basement boundaries to depths over 2.5 km in resistive environments. 1D, 2D, and 3D inversions of MobileMT data provide detailed images of subsurface resistivity contrasts useful for mineral exploration targeting.

1. MobileMT
airborne surveys
from innovations to discoveries
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2. Presentation Outline
• Motivation of the next generation of airborne AFMAG development
• Principles
• MobileMT - technical solutions and characteristics
• Field examples
• Forward modeling of challenging cases
• Available inversions
• Discussion
2 Presentation Outline

3. motivation
• Limited depth of investigation of systems with controlled EM
field sources, especially in conductive environment or complex
terrain;
• Limited resolution, bandwidth, and sensitivity to any direction
of geoelectrical boundaries of previous airborneAFMAG
systems in commercial use;
• Latest achievements generally in electronics, digital
technologies for the last 10-15 years, since the lastAFMAG
development.
3 Motivation of the next generation of airborne AFMAG development

4. principles
4 MobileMT measurements principles
Air
Earth
X
Y
Z
H Receiver in air
E Base station on the ground
𝑯𝒙
𝑯𝒚
𝑯𝒛
=
𝒀𝒙𝒙 𝒀𝒙𝒚
𝒀𝒚𝒙 𝒀𝒚𝒚
𝒀𝒛𝒙 𝒀𝒛𝒚
𝑬𝒙
𝑬𝒚
𝛔 = 𝛍𝛚|𝒀 𝟐
|
data time series
H поле
E поле

5. Technical features and advantages
• MobileMT - first airborne AFMAG system with electric
component (base station) and consisting of independent
”signal” and “reference” channels what provides bias-free
data
• 3 component towed magnetic receiver eliminates the
problems of spatial orientation in the air and related
noise
• MobileMT's electromagnetic data is digitized and
recorded at 74 kHz. It accumulates the input quantity over
a defined time to produce a representative output for
high quality data processing.
5 MobileMT technical advantages
Ex
Rx
Ey
Ry

6. 0
250
500
750
1000
1250
1500
1750
2000
2250
2500
2750
3000
1 10 100 1000 10000 100000
h,depth,m
ρ,Halfspace resistivity, Ohm-m
34 Hz
42 Hz
53 Hz
67 Hz
84 Hz
106 Hz
134 Hz
169 Hz
213 Hz
268 Hz
337 Hz
426 Hz
536 Hz
676 Hz
851 Hz
1072 Hz
1351 Hz
1702 Hz
2145 Hz
2702 Hz
3405 Hz
4290 Hz
5404 Hz
6810 Hz
8580 Hz
10810 Hz
13619 Hz
17159 Hz
21619 Hz
f, 34Hz
f, 21,619Hz
technical features and advantages
6 Frequency recorded windows and resistivity-depth relation
h = 357 * √(ρ / ƒ), metres
71% of skin depth
10
100
1000
10000
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
Frequency,Hz
Channel
MobileMT recorded frequency windows
0
100
200
300
400
500
600
700
800
900
1000
10 30 50 70 90
Глубинаисследований,м
Ohm-m

7. Field examples- Shea Creek, Athabasca
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Kianna Zone
Basement boundary
Basement boundary
Full range depth
Sandstone depth range
Alteration zone
MobileMT
apparent conductivity
profiles
Typical schematic
Shea Creek
geological cross-
section (after Rhys
et.al., 2010)

8. 8 Add a footer
Field examples- Cochrane, Ontario

9. Field examples Wawa, Ontario,
shear zone
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10. Field example-Thomas Creek Co-Cu porphyry
target (Tasmania)
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MobileMT
visible copper sulphides from 199m to 298m depth

11. 11
4/22/202
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MobileMT depth of investigation in resistive environment is 2.5 km
2d inversion of MobileMT data

12. MobileMT forward modeling in the conductive
environment. Case I - Porphyry
1
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Emond, A.M., Zhdanov, M.S., and Petersen, E.U.(2006). Electromagnetic modeling based on the rock physics description of the true complexity
of rocks: applications to study of the IP effect in porphyry copper deposits. SEG/New Orleans Annual Meeting. Expanded Abstracts.
a typical porphyry copper system in the southwestern U. S.

13. MobileMT forward modeling in the conductive
environment. Case II - Kimberlites
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Arkhangelsk region. Russia
Kimberlite pipe 478b
(Stogny, Korotkov, 2010)
Model
calculated
Field
inversion

14. 1 4/22/202
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low sulphidation epithermal gold deposit
Model (after Williams, 1997)
Calculated
MobileMT
response
Constraining the silica cap (2000
Ohm-m) during the inversion makes
the rest part of the section closer to
the original model.
Non constrained inversion
Case III

15. Available inversions of MobileMT data
15 free and fast 1D inversion a footer
1D nonlinear least-squares iterative inversion
developed by Nikolay Golubev for MobileMT.
The inversion algorithm is based on the
conjugate gradient method with the adaptive
regularization (Zhdanov, 2002).

16. 16 2D inversions
Available inversions of MobileMT data
2D inversion
Detail and goal-oriented inversions based on
adaptive finite elements and regularized non-
linear MARE2DEM, focusing on specific zones of
interest (Kerry Key,Jeffrey Ovall. A parallel
goal‐oriented adaptive finite element method for
2.5‐D electromagnetic modelling. Geophysical
Journal International.Vol.186, Issue 1. 2011.).

17. 17 3D inversions
Available inversions of MobileMT data
3D inversions

18. Conclusions
The latest development in airborne EM passive fields,
MobileMT, has the following advanced features:
• 4 orders of frequency measurement range reflecting near
surface and deep geological structures;
• the broadband range is divided on up to 30 collected
frequency windows what provides data selection
capabilities and high in-depth resolution;
• Inferring geoelectrical structures in absolute conductivity
units (magnetic and electric components);
• Resolving resistivity contrasts between geological units in
any direction including layered geology (total field
through three geometrical components).
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19. Thank you for attention!
info@expertgeophysics.com www.expertgeophysics.com
acknowledgements:
Accelerate Resources Ltd.,
MacDonald Mines Exploration Ltd.,
Promiseland Exploration Ltd.
(data and permission)