Abstract

The 14.4-Mt Lalor copper-zinc-gold deposit situated in the Flin Flon Greenstone Belt of north-central Manitoba is large (>900×700m) but deeply buried (>5501200m) and was discovered using deep penetrating ground fixed-loop time-domain electromagnetic (EM). Results from three different airborne EM surveys over a five-year span permit comparisons of the system responses over the Lalor volcanogenic massive sulfide deposit region, assisted using 1D-2D-3D inversions. In late March, 2007, soon after its drilling discovery, Hudson Bay Exploration contracted Geotech to fly helicopter versatile time-domain electromagnetic (VTEM) surveys over the region west of Snow Lake, Manitoba. The deposit was not detected due to its large depth of burial (>550m) and the lack of magnetic response. In 2009, Geotech carried out a helicopter z‐axis tipper electromagnetic (ZTEM) passive EM test survey over the Lalor deposit, which was successful and led to a larger survey over the area. In 2012, a second VTEM survey test was flown, using the more deeply penetrating VTEMMAX system. Although it had sufficient penetration to detect the orebody, on-site mine-site development appeared to overprint the deeper VTEMMAX deposit response. However, a deep (>500m) conductive anomaly from a stringer sulfide occurrence, known as South Bull’s Eye, which lies south of Lalor, was well resolved in the ZTEM and VTEMMAX surveys.

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