The document summarizes airborne EM and magnetic geophysical survey data and inversion results over an area in Canada. The inversions identified low amplitude magnetic and conductivity anomalies within the survey area. Based on the geophysical data, further soil sampling and prospecting are recommended over the anomalous trends to better understand the geology, and physical property measurements on rock samples are needed to aid interpretation.

1. Wicheeda North Project EM and
Magnetics Inversion Results and
Interpretation
Prepared for International Montoro Resources
Inc.
By Sean Walker
May 2019

2. Executive Summary
• Airborne AeroTEM time domain EM, magnetics, and
radiometrics survey flown over a single block in 2010.
• 2011 interpretation of the data highlighted anomalies
within the block
• New area was staked in 2018 (partial coverage of
Chuchinka block)
• The EM and magnetics data were inverted to produce a 3D
voxel models
• Resulting conductivity trends and low amplitude
magnetization anomalies should be followed up with
prospecting and/or soil sampling
• Physical property measurements recommended for
representative rock samples collected within the area

3. 2011 Magnetics Interpretation (1)
• AeroTEM magnetics data flown in 2010
• 50 m line spacing, mean terrain clearance of magnetometer 88 m
• Dominated by regional trend 1 km map grid

4. 2011 Magnetics Interpretation(2)
• Linear trend (top left) removed from
magnetic data to calculate residual (lower
left), second vertical derivative (lower right)
highlights discrete features
• AeroTEM magnetics interpretation (green
polygons) from 2011 show: magnetic
“high” features 1-5 and magnetic “low”
features A and B.
• The anomalies present are very low
amplitude < 5 nT
• Only part of anomaly “B” lies within the
current IMT claim block
1 km map grid
Linear trend
Residual
magnetics

5. Magnetics interp. comments (1)
• More careful regional trend removal can
affect the data significantly.
• Regional trend > 1 km (top left) removed
from magnetic data to calculate high pass
filtered TMI (lower left). The linear trend
residual magnetics are shown for
comparison
• The low feature “B” is no longer present
and was likely part of the regional trend
• The remaining anomalies are very low
amplitude < 5 nT
1 km map grid
1km high pass
residual
1km high pass
magnetics
Residual
magnetics

6. Magnetics interp. comments (2)
• Second vertical derivative (2VD)
highlights discrete anomalies
• The 2011 processing used upward
continuation to suppress some
high frequency features. The
upward continued 25m 2VD is
shown top left.
• This can also be accomplished via
wavelength filtering. Low pass
filtered 2VD data is shown bottom
left.
• The shape of the main anomalies
in the data is retained. The low
pass filtering results in a less sharp
image, however many of the
artefacts have been suppressed.
1 km map grid
Up25 m
2VD
LP 215
2VD

7. Magnetics interp. comments (3)
• The data used in the 2011
interpretation (top left) contains
features that are likely due to
regional trends and high frequency
“noise”.
• The data was band pass filtered
(lower left) in order to suppress
these features.
• Unfortunately, this has resulted in
the removal of Anomaly B. The
remaining features are all low
amplitude.
1 km map grid
Residual
magnetics
Band pass
filtered

8. Magnetic Inversion Overview (1)
• Survey parameters affecting inversion
– Line spacing: 50 m
– Survey area: 8 x 6 km
– Measurement height: ~88 m
– Mesh cell size: 30 x 30 x 15 m
• Pre-processing applied prior to inversion
– Low pass filter: 215 m (~4 x cell size)
– High pass filter: 1 km (based on regional trends)
– Upward continuation: 0 m
– Data down-sampled: 1 reading per 30 m
– Mean value removed
– Noise added: random, zero mean, std dev = 0.158 nT

9. Magnetic Inversion Overview (2)
Short wave length features
removed before inversion
Long wavelength features
removed before inversion
1 km map grid

10. Magnetic Inversion Overview (3)
• The filtered, mean
removed, noise added
magnetic data is used in the
inversion
1 km map grid

11. Magnetic Inversion Overview (4)
• The data was inverted using Geosoft's VOXI
Magnetic Vector Inversion software.
• Multiple inversions were carried out in order to
find a model that fit the observed data within the
allocated noise threshold while not adding
unnecessary features to the model.
• The final model is the amplitude of the
magnetization vector normalized to the induced
field strength. This results in a model with units
equivalent to SI susceptibility.

12. Magnetic Inversion Results (1)
Error estimates Data misfit
1 km map grid
• Error estimates are low <0.5 nT
• Data fit is good overall (standard deviation of 1).
• Misfit is randomly distributed

13. Magnetic Inversion Results (2)
100 m depth slice 200 m depth slice
1 km map grid

14. Magnetic Inversion Results (3)
300 m depth slice 400 m depth slice
1 km map grid

15. Magnetic Inversion Results (5)
3D Magnetization Amplitude Iso-surfaces. Gray: 0.0001 Blue: 0.0002, Green 0.0003, Yellow 0.0004, Red 0.0005 (all units
Equivalent SI)
View: Azi 0, Incl 60

16. Magnetic Inversion Comments (1)
• The strongest magnetization amplitude
anomaly is at the edge of the survey (blue
polygon) 800 x 200m, ~ 100 m deep.
• Important caveats:
– Anomalies at the edge of grids can sometime
be artefacts of the trend removal process
– The largest amplitude in the anomalous zone
is 0.5 x 10-3 SI. It will likely be difficult to
detect variations this small when using a hand
held magnetic susceptibility meter or rock
and/or core samples.

17. 2011 EM Interpretation (1)
• AeroTEM time domain EM data flown in 2010
• 50 m line spacing, mean terrain clearance of EM bird 50 m
• 16 times gridded as time channels
• Six weakly conductive trends identified from the data 1 km map grid

18. 2011 EM Interpretation(2)
• Blue lines indicate thick (or flat lying) conductors
and red lines indicate thin (or steeply dipping)
conductors
• All of the anomalies are characterized as weakly
conductive as the majority of the signal has
decayed away by the mid-time channels
• The thin conductors could represent faults
• The “thick” conductors do not show
characteristics of discrete bedrock conductors
(sharp edges) and are more likely the result of
thickening flat lying conductive units (sediments?)
1 km map grid
Very early
time
Early
time
Mid
time

19. TEM Inversion Overview (1)
• Survey parameters affecting inversion
– Line spacing: 50 m
– Survey area: 8 x 6 km
– Measurement height: ~50 m
– Mesh cell size: 25 x 25 x 4 m
• Pre-processing applied prior to inversion
– Area split into two blocks
– Data down-sampled: 1 reading per 50 m
– Negative data removed
– Data units converted from nT/s to pV/(Am4)
– Noise estimate: max(0.05*abs(datum), 0.02)
– Starting and reference model: 1 x 10-4 S/m

20. TEM Inversion Overview (2)
• The data was split into two areas and inverted
using Geosoft's VOXI Time Domain EM Inversion
software.
• Multiple inversions were carried out in order to
find a model that fit the observed data within the
allocated noise threshold while not adding
unnecessary features to the model.
• The final conductivity model from the two areas
were merged into a single voxel.
• The final model is the conductivity with units of
S/m.

21. TEM Inversion Results (1)
50 m depth slice 100 m depth slice
150 m depth slice
1 km map grid

22. TEM Inversion Results (2)
3D Conductivity Iso-surfaces. Yellow 0.001, Red 0.003 (all units S/m)
View: Azi 0, Incl 60

23. TEM Inversion Comments (1)
• Moderately conductive zones were recovered at
each of the thick trends. Since the inversion uses a
stitched 1D inversion it is not possible to accurately
recover the thin targets.
• Trend 1 is spatially coincident (in an X-Y sense) with
the magnetic anomaly identified during the MVI
inversion.
• Target 2 and Target 3 also fall within the IMT claims.
• The conductivity values are quite low (3 x 10-3 S/m)

24. Summary
• The 2011 interpretation of the airborne TEM and magnetics data provided
a qualitative assessment of the magnetic bodies and lineaments in the
survey area
• The magnetization vector and time domain EM inversions carried out have
recovered models which provide a distribution of magnetic and
conductive material that can be included in a quantitative interpretation
• The anomalous magnetization within the claim block is very low
amplitude.
• There are two anomalous flat lying conductivity trends and one thin
(vertical) trend within the claim block. The trends do not appear to be
related to drainage and strike in a direction similar to the Chuchinka Group
as mapped in the regional geology.
• The pattern of responses do not match the characteristics of carbonatites
(circular, intrusive) described in the IMT 43-101 report (Lane, 2019)

25. Recommendations
• Further soil sampling and prospecting are
recommended over the anomalous trends.
• Physical property measurements should be
carried out on rock samples of the main
geological units within the claims. This data can
help provide a better understanding of the
geophysical responses in relation to the geology.
It may also reveal physical property contrasts that
can be used to determine if other geophysical
methods could be applied in the area.