First look at data from a three-dimensional audio-magnetotelluric survey at the McArthur River mining camp, northern Saskatchewan

Abstract

As part of EXTECH IV, three-dimensional audio-magnetotelluric data were collected in the McArthur River uranium mining camp, northern Saskatchewan. One hundred and thirty five audiomagnetotelluric stations were acquired along 11 profiles over the P2 and P2 North mineralized zones with an average site spacing of 300 m. The new audio-magnetotelluric data extend the coverage of an earlier two-dimensional survey and were acquired to provide a three-dimensional view into the subsurface conductivity structure of the McArthur River deposit, the overlying Athabasca Group sandstone, the basement rock types and offsets, and the alteration assemblages associated with the deposit. Digital comb filters were tuned to and removed strong harmonics; then robust audio-magnetotelluric responses were calculated. The resulting induction arrows map different domains of coherent and complex electrical strike. Data qualities and distribution are ideal for the next stage-calculation of a three-dimensional audio-magnetotelluric model.

Three-dimensional inversion of magnetotelluric data for mineral exploration: An example from the McArthur River uranium deposit, Saskatchewan, Canada

“…4; Craven et al, 2003). The average spacing of measurement locations along the lines was 300 m. The average separation between lines was approximately 800 m. The lines were oriented north-west to south-east to be perpendicular to the general strike of the graphitic basement fault zone.…”

“…The survey area was approximately rectangular, with dimensions 5 by 8 km. Data were acquired in the frequency range from 1 to 20,000 Hz using three Metronix 24-bit ADU-06 systems with Geosystem AMT magnetic sensors (Craven et al, 2003). One system was deployed in a culturally quiet location and used as a fixed reference.…”

“…The spatial correlation of the uranium deposits with zones of graphite, and the high conductivities of the graphitic zones relative to both the metamorphic rocks of the basement and the sedimentary rocks of the basin, has meant that electromagnetic techniques have been the favoured methods when prospecting for further deposits. This continues to be the case, with, for example, the use of new airborne time-domain electromagnetic systems to efficiently investigate the upper 200 or 300 m of the subsurface around the edges of the Athabasca Basin (Cristall and Brisbin, 2006), and the use of audio-magnetotellurics (AMT) to investigate down to a couple of kilometres towards the centre of the Basin (Craven et al, 2003;Leppin and Goldak, 2005;Tuncer et al, 2006).…”