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.
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.
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.
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.
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.
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.
Gravity surveys are completed for a number or applications, including mineral exploration (e.g., diamonds) and geotechnical investigations (e.g., escarpments).
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.
The IMAGEM system supported by Devbrio Géophysique Inc. is a state-of-the-art high resolution time-domain system that is capable of recording 200 channels of on- and off-time EM measurements.
Geotechnical engineers require accurate parameters for designing buildings, foundations, rock slopes and so forth. The shear-wave velocity of the ground is a useful part for determining common geotechnical parameters such as Poisson's Ratio and Shear Modulus.
ClearView is in the arctic carrying out snowmobile-mode geophysical surveys. These surveys are faster than walking mode, safer, more accurate, higher quality and much higher resolutions than airborne surveys. The project this year is focused on helping exploration geologists pick near-mine targets for further evaluation.
We are proud to say that ClearView Geophysics Inc. has provided professional geophysical services for mineral exploration, environmental investigations and geotechnical applications since it was incorporated in 1996.
ClearView was founded by Joe Mihelcic, geophysicist, after completing his MBA at Ivey Business School in London, Ontario. Since then, ClearView has employed and trained dozens of high-calibre geoscience students, technicians, engineers and specialists. The company was established to allow greater flexibility in applying customized solutions.
Here's to the next 20 years!
Sometimes the simplest and most inexpensive methods from Civil 101 can provide surprisingly high accuracy vertical positioning. ClearView recently completed an elevation survey to complement a complex series of geophysical surveys at a site in Southern Ontario. The elevation data was used to provide 3D capabilities for presenting the geophysical data. A pair of Trimble ProXT GPS receivers were used to provide accurate temporary benchmark data. The level survey data closed to less than 1/8 of an inch over 700 metres in both directions through the 1400 metres long survey area.
MaxMin by Apex is a mature method used over many decades for mineral exploration. ClearView is presently applying the method on a gold exploration project to see if it can detect subtle quadrature (out-of-phase) responses that might indicate stringer mineralization, faults or geologic formation variations.
There are many types of 'targets' that geophysics can be used to detect. For exploration, targets can be gold, base metals, speciality metals, diamonds and sand/gravel deposits, to name a few. Each target type has its own unique response to geophysical methods based on its local geologic environment - this is called its 'geophysical signature'.
The Dipole-Dipole electrode configuration is ideal for detecting off-hole targets because the transmitter and receiver electrodes are always at the same distance apart as the configuration moves down the borehole. This makes detecting anomalies easier because if there weren't any, the resistivity profile would be flat in a uniform half-space.
Snowmobile-mode surveys can be used with different geophysical techniques. Our flagship survey is the cesium-magnetometer survey - almost continually applied and operated in the arctic on small and large-scale projects at spring-time personally by Mr. Mihelcic since 1996. Only the mag sensor and GPS dome are on the sleigh separated by 1.7 metres. Post processing corrections using in-house software correct for this layback and a 0.33-second system latency which is confirmed by speed tests done over anomalies in both directions. The tried and true un-manned aluminum sleigh is located far back from the snowmobile. It has proven durable in boulder fields, steep terrain, extreme cold and wet conditions.
These design features, fine-tuned over 20 years, give extremely low heading errors - far better quality than walking mode and certainly higher resolution than any airborne survey. Productions rates of 40-80 km per day can be acquired depending on terrain, with readings at 10x per second.
This spring we applied a combined cesium-mag and TDEM system on a large-scale project in Nunavut.
The image below shows the magnetometer sleigh followed by the TDEM sleigh on the horizon:
ClearView is a registered member of ISNetworld. Many clients use ISNetworld to choose their suppliers so that they can be sure all requirements are met. For example, ClearView carries $5-million coverage for commercial liability and professional insurance.
Many cesium magnetometer surveys are carried out without cut lines. The onboard GPS is used for navigation and positioning. Data are recorded at 10x per second. Therefore, lines are spaced 50-metres apart in areas where drills are standing by. This allows for the interpretation of 'breaks' in the mag which can act as conduits for gold and other economic mineralization. Gone are the days where traditional 'proton precession' style magnetometers are used for serious high resolution and high quality data. IP/resistivity survey lines can be 'targeted' to specific areas (e.g., breaks in the magnetics contours) to reduce costs by exploring more efficiently!
ClearView completed several 4-Pin Wenner Array surveys as per ANSI/IEEE Std. 81-1983 and others as a guide (i.e., IEEE 80-2000 and ASTM G57 for soil resistivity test). The work was carried out so that appropriate electrical grounding design for planned facilities within highly congested industrial areas in downtown Toronto could be done.
ClearView Geophysics recently completed Resistiviy Imaging, EM, and GPR surveys in the arctic. The purpose of the work was to determine depth to bedrock and areas of potential frost heave from ice wedges to assist with plant design and construction. The work was done with multiple GPR frequencies and resistivity electrode spacings using a Syscal Pro with 96 electrodes. This combined-methods approach, typical on ClearView projects, makes it possible to provide a more definitive interpretation of the sub-surface. High near surface resolution and good depth penetration to over 60 metres were obtained over an area of 25 hectares in less than 2 weeks.
ClearView owns Sensors & Software 100 MHz, 250 MHz and 500 MHz systems...this image shows great resolution, but penetration is not very deep using 250 MHz...
The spectral really helps with quickly weeding unstable decays versus good ones, and the good ones are used to help with fine-grained/disseminated vs. Coarse-grained/linked sulphides.’
The main thing with our cross-hole IP system is that it’s simple, with single wires down each hole, and there are many readings taken at different angles making the inversion converge very quickly even with tight constraints (e.g., UBC low chi factor). Just a couple of off-the-shelf winches and new IP wire. We mark the wire at 10-metre intervals as slippage on the counter is inevitable.’