September 16, 2009
VTEM detects the Night Hawk Lake conductor from 705 m above.
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March 24, 2009
BENTON RESOURCES, ROYAL ROADS & GOLDEN DORY APPROVE 2009 PROGRAM FOR LONG RANGE NICKEL JOINT VENTURE, NEWFOUNDLAND – DRILL TARGETS IDENTIFIED
"... Among the targets selected for further work is a 600 metre long VTEM conductive anomaly described by Geotech Ltd. as “a relatively strong conductor consistent with massive sulphides”. This target has been selected for testing by diamond drilling, and it is anticipated that additional targets will be developed from results of the prospecting and ground geophysical surveys."
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Equipment
A typical Geotech airborne geophysical system consists of the following main components:
- A time-domain electromagnetic system (VTEM)
- A high-sensitivity cesium magnetometer
- A GPS navigation system
- A radar altimeter
- A cesium magnetometer base station
1. VTEM System
Geotech's time-domain electromagnetic system (VTEM) utilizes modern advances in digital electronics and signal processing along with recent company research in the area of precision electromagnetic measurements.
1.1 The system was designed to have very low-noise characteristics. This low-noise level is as important as the large transmitter dipole-moment in determining the capabilities of the system:
- Deep penetration
- High spatial resolution
- Excellent resistivity discrimination
- Detection of weak anomalies
Recent surveys flown with the Geotech system have picked up a number of anomalies left undetected by previous airborne EM surveys. The Geotech VTEM system flew the Reid-Mahaffy, Caber, Perseverance and Montcalm test ranges. The results of the tests have demonstrated that Geotech VTEM system provides the industries highest signal/noise ratio and spatial resolution of conductors. The receiver and transmitter coils are concentric and Z-direction oriented.
1.2 The system was designed to be versatile and adaptable to different geophysical priorities such as deep penetration or for different resistivity ranges.
1.3 The system is easily transportable. It can be packaged into relatively small units for shipping to distant survey areas. The transmitter-loop can be assembled or disassembled in 3-4 hours.
1.4 The system is completely modular, allowing for easy replacement of any part in the field. This is extremely useful if the EM loop sustains damage.
2. Magnetometer
A Geometrics/Scintrex split-beam total-field magnetic sensor, with a sampling interval of 0.1 seconds and an in-flight sensitivity of 0.02 nT, is utilized. The magnetometer will perform continuously in areas of high magnetic gradient with the ambient range of the sensor approximately 20k-100k nt.
3. Electronic Navigation - GPS
A Geotech GPS navigation system utilizing NovAtel's WAAS (Wide Area Augmentation System) enabled OEM4-G2-3151W GPS receiver provides in-flight navigation control. This system determines the absolute position of the helicopter in three dimensions by monitoring the ranges to orbiting satellites. As many as 11 GPS and two WAAS satellites may be monitored at any one time. The positional accuracy or circular error probability (CEP) is 1.8 m, with WAAS active, it is 1.2 m.
4. Altimeter
A radar altimeter system records the ground clearance to an accuracy of approximately 1 m.
5. Data Acquisition/Recording System
A custom Geotech data acquisition system is used. Data is recorded onto PCMCIA flash cards.
6. Field Computer Workstation
A dedicated PC-based computer workstation is used in the field for purposes of displaying geophysical data for quality control, calculating and displaying the navigation, producing preliminary EM anomaly information and magnetic maps, and copying/verifying the digital data.
7. Base station
A dedicated computer including high-sensitivity base station cesium magnetometer is employed to record magnetic diurnal activity.