From tree-tops to massive sulphide in the Mabel Lake area, British Columbia, Canada

Glacial deposits, dense vegetation and rugged terrain pose challenges to conventional mineral exploration in the Mabel Lake area of southern British Columbia, where metamorphosed schists, quartzites and calcareous rocks of the Monashee sequence are known to host significant Pb-Zn deposits such as Kingfisher and Ruddock Creek. In 2006, the Geological Survey of Canada conducted a reconnaissance tree-top sampling programme to provide a biogeochemical dataset for c. 700 km(2) of this region. Douglas-fir tree-top samples from 562 sample stations were collected from a helicopter, and analysis of the tissues indicated several Tl and Cd anomalies. Detailed follow-up sampling east of Mabel Lake using western hemlock bark confirmed a Tl anomaly extending c. 600 x 600 m. Data from these surveys were published but received little attention for several years until the area surrounding the main Tl anomaly was staked and detailed exploration commenced. Ah soil horizon sampling within the Tl anomaly identified multi-element anomalies including high concentrations of Mo and Zn. Indicator minerals from a few stream sediments included gahnite and goldmanite providing further evidence for the presence of base metal mineralization. Follow-up work that involved 391 m of excavations along 3 parallel trenches revealed a gossan-rich zone, 10-35 m wide and >50 m long with best concentrations of 8.98% Zn (over 3 m); 580 ppb Re; 1339 ppm Mo, and anomalous concentrations of Cd, Cu, Bi, Ni, Pb, Sn, Tl, V and W. Subsequently, a HeliTEM (R) electromagnetic survey was flown over c. 12 km(2) of the contiguous claims and a small drilling programme has intersected Zn-rich massive sulphide. This grassroots study demonstrates the evolution of an exploration programme that started with a chronological order of: (a) reconnaissance biogeochemical survey; (b) detailed biogeochemistry; (c) Ah soil horizon geochemistry; (d) indicator mineral stream sediment survey; (e) trenching; (f) airborne geophysics; and (g) drilling that has identified significant base metal mineralization.