ZTEM and VTEM airborne EM and magnetic results over the Lalor copper‐gold volcanogenic massive sulfide deposit region, near Snow Lake, Manitoba

Abstract

The 14.4-Mt Lalor copper-zinc-gold deposit situated in the Flin Flon Greenstone Belt of north-central Manitoba is large ([Formula: see text]) but deeply buried ([Formula: see text]) 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 ([Formula: see text]) 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 [Formula: see text] system. Although it had sufficient penetration to detect the orebody, on-site mine-site development appeared to overprint the deeper [Formula: see text] deposit response. However, a deep ([Formula: see text]) 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 [Formula: see text] surveys.