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Summary In July 2008, Indicator Minerals flew a high resolution magnetic gradient survey near Kugaaruk, Nunavut looking for kimberlite deposits. This survey was designed as a potential replacement for ground-based geophysics with a higher data resolution and collection speed. High altitude data was originally collected over the area in 2005, with follow-up ground surveys. The high resolution magnetic gradient system used was the Battelle VG- 16, which was designed for UXO detection. Several modifications were made to the system, the survey methodology and the data processing to optimize this UXO system for mineral exploration. Several of the survey blocks were covered with the three different techniques including high-altitude airborne, lowaltitude airborne and ground-based magnetics, allowing for a comparison of the results to demonstrate the trade-offs between the three. Introduction Airborne magnetic surveys are a staple exploration technique for diamondiferous kimberlites, especially in the Canadian Arctic. Surveys using helicopter-towed birds or stinger-mounted fixedwing configurations map geologic features from 30m to 50m altitude. Line spacing is generally 50m to 150m depending on the sensor altitude and the individual target objectives. Geophysical anomalies and geologic features of interest are selected for follow-up using ground-based techniques. These are conducted with man- or vehicle-portable systems using line spacing between 20m and 50m to provide higher resolution, particularly of near-surface features. A new helicopter-mounted magnetic gradiometer array was tested as a substitute for ground-based systems in July 2008. Originally designed for the detection of unexploded ordnance, this system offers a potential line spacing and sensor altitude of less than 2m. Actual survey altitudes are controlled by local topography and vegetation but could average 3m to 5m at most sites above the tree line. The Barrow Lake site, some 50km SE of Kugaaruk, Nunavut, contained targets including kimberlite dikes and sills. These narrow features were ideal targets for the low altitude airborne system. The survey covered several blocks which had been previously been flown with conventional aeromagnetic techniques. Some of the blocks had also been covered by ground surveys. A comparison of the three showed no signs of kimberlites, but the low-altitude helicopter data was shown to have the highest resolution. Geology The Barrow Property is located on the southern Boothia Peninsula and the Northern Wager plateau (Bostock, 1969) and is underlain by 1.67 to 1.63 Ga gneissic rocks of the Bothia Horst which is believed to be the northern extension of the geologic Churchill Province (Kerr, 1977). Locally, the uplifted basement rises 300 m and forms the Parke Hills which are dissected by steeply-dipping, north trending faults. The terrain is rugged and glacially scarred. Large boulders and rock-basin lakes are scattered throughout the region (Figure 1).The survey area is located within the Arctic Circle well above the tree line. This area is of interest due to possible kimberlitic intrusions pointing to a potentially diamondiferous mantle (Kienlen et al., 2008). The purpose of this survey was to further map and investigate the site geology, particularly any intruding kimberlites and kimberlite related structures.
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A small conductive massive sulfide body in northern Ontario was used as a test site to compare airborne, semiairborne The x-, y-and z-component dB/dt data for the magenta line and ground electromagnetic systems. The are shown on Figure 2. The airborne and semi-airborne airborne system had the lowest signal to noise ratio over the systems can also output the B-field response using the body (25), the ground system had the highest ratio (50000), method described by Smith and Annan (1999). Because and the semi-airborne system was intermediate between the the ground system used in this experiment can only other two (500). For a deeper conductor, the differences measure dB/dt, our comparison and our discussion is between the ground and semi-airborne systems would not restricted to that type of data. The airborne data presented be so marked. In logistical difficulty, the semi-airborne in Figure 2 have undergone a minimum of processing: the system is also intermediate between the other two systems, data have been lagged, so that the plotting point is the in that an aircraft replaces ground crews, but some loop receiver position, and a nine point median filter (of width laying is still required.
SUMMARY In 1980 a large airborne gamma-ray spectrometer survey was flown in Malaysia. In 1991 these data were reprocessed to remove levelling problems and to enable the airborne data to be more effectively utilized. The airborne data were back-calibrated to convert the airborne measurements to ground concentrations of potassium, uranium and thorium. This was achieved by comparing the airborne measurements with ground measurements using a calibrated portable gamma-ray spectrometer. INTRODUCTION In 1980 the Government of Malaysia funded an airborne magnetic and spectromehic survey over a large area of Peninsular Malaysia.
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The first AGRS developed at the GSC (BRISTOW ant recorded airborne experiments were conducted in DDNHOFFER, 1968) was a digital four channel Canada in 1947 by Eldorado Mining and Refininu Ltd. spectrometer system. A?? of the processinn was donr a Canadian CrownCorporation (Gregory 1955).
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Hitchman et al. (1998) used a model developed by Campbell et al. (1989) based on the Base station subtraction is one possible method for 1965 International Year of the Quiet Sun to derive global correcting temporal variations occurring during magnetic curves of Sq total-field variations. Their results show that surveys. A field experiment comparing two base stations total-field variations have a seasonal variability and distinct separated by 88 km on a quiet day shows that the field at latitude dependence. There is a pronounced maximum in one base station cannot predict the field at the other. The the daily variation at the equator, and, in both hemispheres DC difference is approximately 107 nT and the non-DC on either side of this maximum, there are bands where the residual is a few nT. Furthermore, in a second field amplitude of total-field variations is subdued.
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