none 10.1190/1.3343573 Society of Exploration Geophysicists Society of Exploration Geophysicists 186 41725824 5981 2025121115212291000 10.1190 2025-12-11T20:21:29Z 2010-03-23T18:04:03Z 17 Geophysics 1942-2156 0016-8033 2010 01 01 2010 75 2 Marc A. Vallée 1Fugro Airborne Surveys, Ottawa, Canada. E-mail: mvallee@fugroairborne.com. Richard S. Smith 2Formerly Fugro Airborne Surveys, Ottawa, Canada. Presently Laurentian University, Sudbury, Canada. E-mail: rssmith@laurentian.ca. Pierre Keating 3Geological Survey of Canada, Ottawa, Canada. E-mail: pkeating@nrcan.gc.ca. Abstract Exploration for volcanogenic massive sulfides requires good geologic understanding. Geologic knowledge often is limited by a lack of outcrops. This is especially true in Canada under residual glacial covers. Geologic information must therefore be complemented by information obtained using means such as geophysical and geochemical observations. Electromagnetic (EM) methods extend lithological understanding to depths beyond the overburden. Massive sulfides are highly conductive and, depending on their depth and volume, may be detected easily by airborne EM surveys. They are more often equant than graphitic sediments, which typically have longer strike length. Current EMtechniques that identify massive sulfides operate in the frequency or time domain, the latter being more common. Additional information can be provided by using power-line fields as a source of EM signals when the powerlines are appropriately located in the area of interest. We have worked in an active exploration area near Chibougamau, Canada, known for a large occurrence of massive sulfide deposits. The geology is a sequence of volcanic formations with felsic and mafic intrusions. Our magnetic technique responded well to mafic rocks. An airborne time-domain EM survey mapped localized and intrasedimentary conductors in that area. We learned in our study that power-line EM fields can be used to map large-extent conductive formations and narrow geologic faults. 2010 01 01 2010 03 23 2010 B67 B72 10.1190/1.3343573 https://pubs.geoscienceworld.org/geophysics/article/75/2/B67/308309/Case-history-of-combined-airborne-time-domain https://pubs.geoscienceworld.org/seg/geophysics/article-pdf/75/2/B67/3217144/gsgpy_75_2_B67.pdf https://pubs.geoscienceworld.org/seg/geophysics/article-pdf/75/2/B67/3217144/gsgpy_75_2_B67.pdf http://geophysics.geoscienceworld.org/cgi/doi/10.1190/1.3343573 Allard 1979 Stratigraphy and metallogeny in the Chibougamau area Exploration discoveries, Noranda district, Quebec (Case history of a mining camp) Boldy 593 1979 10.4095/106067 Geophysics and geochemistry in the search for metallic ores Environnement géologique de l'extrémité orientale de la sous-province de l'Abitibi Chown 96 1996 Géologie et évolution métallogénique de la région de Chibougamau 5th Decennial International Conference on Mineral Exploration, Proceedings Gibson 713 2007 The VMS model: Advances and application to exploration targeting Gobeil 83 1983 Carte lithostatigraphique de la région de Chibougamau The Abitibi orogenic belt Goodwin 70 1970 10.4095/103465 Symposium on basins and geosynclines of the Canadian Shield 5th Decennial International Conference on Mineral Exploration, Proceedings Keating 863 2007 A comparison between old and recent airborne time-domain electromagnetic surveys flown in the Chibougamau region, eastern Canada 59th Annual International Meeting Labson 138 1989 Airborne resistivity mapping using powerline sources Martin 2005 Towards new discoveries thanks to the application of 3D modeling in the Noranda Camp Airborne electromagnetic methods Palacky 811 1991 Electromagnetic methods in applied geophysics: Application Earth Planetary International Schmucker 7 365 1973 10.1016/0031-9201(73)90061-7 Regional induction studies: A review of methods and results Geophysics Smith 65 1124 2000 10.1190/1.1444805 The realizable resistive limit: A new concept for mapping geological features spanning a broad range of conductances Smith 21 73 2003 The MEGATEM fixed-wing transient EM system applied to mineral exploration: A discovery case history: First Break