Spectral IP and Resistivity

Spectral Induced Polarization & Resistivity surveys (IP & Res) are excellent methods for detecting disseminated sulphide mineralization that could be associated with gold. The surveys are carried out using surface and borehole modes.

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Large Loop TDEM

ClearView Geophysics Inc. owns and operates transient PROTEM receivers and TEM57/67 transmitters built by Geonics. This system has proven itself useful for detecting both good and bad conductor sulphide mineralization located both shallow and 100’s of metres deep.  It is also useful for detecting sources of water.

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Snowmobile-Mode Cesium Magnetics

Cesium magnetometer surveys are carried out using a custom-built sleigh pulled behind a standard snowmobile.  This system has proven itself on numerous large-scale mineral exploration projects during the past 15+ years. 

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Seismic Refraction

Seismic Refraction surveys are typically carried out for depth to bedrock investigations.  The "shot" can be either an explosive or hammer source.  Interpex IXRefraX software is used to process the data.

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Electromagnetic (EM) and Magnetic surveys

EM and Magnetic surveys are perhaps the most common geophysical methods used on mineral exploration and environmental investigations. The most commonly used EM instruments for environmental investigations are the Geonics EM31 and EM61.

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GPR ( Ground Penetrating Radar )

GPR works best in low conductivity areas. Conductive materials (e.g., clay) attenuate the GPR signal to the point that very little depth penetration is achieved. Penetration is greatest in unsaturated sands and fine gravels.

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Gravity

Gravity surveys are completed for a number or applications, including mineral exploration (e.g., diamonds) and geotechnical investigations (e.g., escarpments).

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Geophysical Interpretation

ClearView has extensive experience interpreting airborne and ground-based geophysical data. We use UBC's suite of inversion software to produce 2D and 3D interpretations of total field magnetics and IP/Resistivity data. Post-processing software is also used to produce various derivative datasets and maps.  

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Welcome to ClearView Geophysics

ClearView Geophysics Inc. is a geophysical services company founded in 1996.  There is no better way to collect high resolution sub-surface data than with ground-based sensors or 'boots on the ground'. When you describe your project goals to us, we will design a geophysical survey to help you achieve those goals in the most cost-effective manner possible. Getting ground-based geophysical data is arduous - so we are constantly working to find ways to make it easier, whether its with our snowmobile- and ATV-mode surveys or with exo-skeleton systems for more supportive and safer fieldwork.

Joe Mihelcic, P.Eng., M.B.A.
Geophysicist, President & Owner

About the Owner: Mr. Mihelcic is an Applied Science '88 Geological Engineering (Geophysics Option) graduate of Queen's University at Kingston and '95 MBA graduate of Ivey Business School at the University of Western Ontario in London. He enjoys designing and implementing off-the-shelf components and technologies to make ground geophysical surveys easier and therefore more cost effective. He also writes his own software to streamline processing and interpretation.

Seismic Reflection for Mineral Exploration

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A Geometrics Geode with ability to record up to 65,536 samples per record allows high resolution data to map stratigraphy and structure to depths up to 2 km using a trailer-mounted 800 lb weight-drop system.  A 'seismic gun' is sufficient for shallower investigation depths. 

b2ap3_thumbnail_SesimicReflectionExample.jpg

Based on the table below, assuming a relatively slow velocity of 4000 m/ns, the straight 2-way travel time to reflect against features ~2 km down (~4km travel) is 1 second.  A longer 4 second to 8 second window is sufficient to capture responses due to thicker and slower overburden, for example. 

 

Velocity of Common Rock Types

Rock Type

Velocity [m/s]

Velocity [ft/s]

Unconsolidated Sandstone

4600 - 5200

15000 - 17000

Consolidated Sandstone

5800

19000

Shale

1800 - 4900

6000 -16000

Limestone

5800 - 6400

19000 - 21000

Dolomite

6400 - 7300

21000 - 24000

Anhydrite

6100

20000

Granite

5800 - 6100

19000 - 20000

Gabbro

7200

23600

b2ap3_thumbnail_GeodeSampleRates.jpg

 

The results also depend on the geology (e.g., velocity contrasts) and more importantly the overburden which is why it can be difficult to guarantee we can reach the same depths for meaningful data across the survey area. In some areas we will get better/deeper-looking data than others.  In some areas we may only get shallow or even no information.

 

In the following screen shot, an example of the raw data (pre-filtered/processed) showing mostly surface waves and first arrivals with a 10-metre geophone spacing and 24 geophones to half a second.  Another proposed spread would have twice the number of receivers and longer depth window (e.g., 4-8 seconds).

b2ap3_thumbnail_PreStacked.jpg

 

For a ‘moving line setup’. The pre-stack filtering steps would include:

 

  • Energy normalization: to prepare for the elimination of surface waves (e.g., remove effects of wavefront divergence and damping).
  • Elimination of Surface Waves: These are the high amplitude, lower frequency data that are crucial for MASW work but need to be minimized for reflection work.  Includes FK-filter and band pass filtering where necessary.

 

The following example is what the data should look like after this pre-stack filtering process on the right:

 

b2ap3_thumbnail_Prestack_Filtering.jpg

 

 Then the data are ready for ‘semblance analysis’ which will use some refraction interpretation results for better control. This process is interactive.  The following example is from shallow data but same process applies to the deeper looking data. Its done for every shot. Then a NMO-stack to bring everything together and finally migration and time-depth conversion to get your typical depth-section.  Probably some other filters as required.

 

 b2ap3_thumbnail_Semblance.jpg

 b2ap3_thumbnail_20200218_125037.jpg

Passive surveys, where no active shots are required, can also be considered where many geophones are placed across the property in both dimensions, and micro-tremor data are acquired over a period of time.  Colour-contour plan maps for various depth sections are often sufficiently detailed for broad scale exploration.

 

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