The Meråker survey was done under the same agreement between
The survey was flown by NGU with a 200m line spacing with 90º azimuth. The average speed was 109 km/h and height clearance for the magnetometer and the electromagnetic probe was 45.3m and for the spectrometer was 75.3m. NGU had flown over the same area in 1991 (~4250-line kilometers or 850 Km2, 90º azimuth, 200m line spacing) and the new flight was intended to intercalate the new flight lines with old ones in a way to increase data density and resolution (Figure 1). The magnetic and radiometric data from 2021/22 were merged with the data from 1991, except the electromagnetic survey due to the different type of instruments and incompatible transmission frequencies.
Figure 1. – Meråker survey area with flight paths
Mr.
NGU used a modified Hummingbird electromagnetic and magnetic system installed in a Eurocopter AS350-B3 (LN-OSD) helicopter designed to obtain low level, low speed detailed airborne magnetic and electromagnetic data. The system was supplemented by 1024 channel gamma ray spectrometer to acquire radiometric data. The instrument specifications are listed in Table 1.
The magnetic data were recorded at 0.2 second intervals resulting in approximately 6m average point spacing. The data was visually inspected and spikes were removed and after several corrections were applied before gridding.
The electromagnetic data were recorded at 0.1 second intervals resulting in data with a sample increment of 3m along the ground on average. The electromagnetic system transmits five fixed frequencies and records an in-phase and a quadrature response for each of the four coil sets of the system. The received signals were processed and used for computation of an apparent resistivity.
The radiometric data were recorded at every 1 second intervals giving a point spacing of approximately 30.3m. The radiometric data were processed using standard procedures recommended by
For quality control, the surveys, altitude and navigation data were monitored on four separate windows in the operator's display during the flight while they were recorded in three streams to the PC hard drive.
The above parameters allow for recognizing sufficient details in the data to detect subtle anomalies that may represent mineralization and/or rocks of different composition.
Table 1. Instrument specifications
INSTRUMENT | PRODUCER/MODEL | ACCURACY/SENSITIVITY | SAMPLING FREQUENCY/INTERVAL |
Magnetometer | Scintrex Cs-2 | <2.5nT throug. Range /0.0006nT √Hz rms | 5 Hz |
base magnetometer | GEM GSM-19 | 0.1 nT | 3 s |
Eletromagnetic | Geotech Hummingbird | 1-2 ppm | 10 Hz |
Gama spectometer | Radiation solutions RSX-5 | 1024 ch's, 16 litres down, 4 litres up | 1 Hz |
Radar altimeter | Honeywell/KRA-10A | ±5ft 40-100 ft; ±5% 100-500ft; ±7% 500-2500ft | 1 Hz |
Pressure/temperature | Honeywell PPT | ±0.03% FS | 1 Hz |
Navigation | Topcon GPS-receiver | ±5 meters | 1 Hz |
Acquisition | NGU custom software |
Mr. Paulo Nuno De Sa Caessa, EurGeol., VP Exploration, who is the Qualified Person for
ON BEHALF OF THE BOARD OF NORRA METALS CORP.
Per: "Minaz Devji"
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