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

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 audio magnetotelluric 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 conduc tivity 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 result ing 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. Resume : Dans le cadre du programme EXTECH IV, on a recueilli des donnees audio magnetotelluriques tridimensionnelles dans le camp minier uranifere de McArthur River, dans le nord de la Saskatchewan. Les donnees ont ete recueillies a 135 stations espacees en moyenne de 300 m, le long de 11 profils recoupant les zones mineralisees P2 et P2 North. Ces nouvelles donnees audio-magnetotelluriques, qui etendent la couverture d’un leve bidimensionnel anterieur, ont ete recueillies afin de representer en trois dimensions la structure de la conductivite du sous-sol liee au gisement de McArthur River, aux gres sus-jacents du Groupe d’Athabasca, aux lithologies du socle et a leurs rejets transversaux, ainsi qu’aux assemblages d’alteration associes au gisement. Des filtres en peigne numeriques ont ete ajustes sur un puissant signal harmonique afin d’en eliminer les effets; on a ainsi pu calculer de solides reponses audio magnetotelluriques. La carte des vecteurs d’induction qui a ete elaboree permet de representer differents domaines ou les directions electriques sont coherentes ou complexes. La qualite et la repartition des donnees sont ideales pour entreprendre l’etape suivante : le calcul d’un modele audio-magnetotellurique tridimensionnel. 1 Contribution to the Targeted Geoscience Initiative (TGI) 2000–2003. 2 Contribution to the 2000-2003 EXploration Science and TECHnology [EXTECH IV], Athabasca Uranium Multidisciplinary Study [AUMS]