The area is underlain by rocks of the Lower Jurassic Unuk River Formation, Hazelton Group. These rocks consist of sandstone, wackes and shale overlain by lapilli tuff of andesitic composition. The Brucejack fault and associated splay faults cut the country rock in a north-south to northwest direction. North of Brucejack Lake, the fault system is bounded on the east by rocks of the Lower Jurassic Betty Creek Formation, Hazelton Group. A variety of Jurassic horn- blende syenites and alkali feldspar syenites occur in the area.

The Electrum Zone consists of numerous subparallel quartz veins occurring in moderate to intense quartz-sericite-pyrite altered syeno- diorite. These veins range from less than 1.0 centimetre up to 50 centimetres in width. Some of the thicker veins can be traced for 50 metres. The veins generally trend 330 degrees and dip steeply to the south. The intrusive consists of from 5 to 8 per cent coarse, sub- hedral, disseminated pyrite.

Surface exposures and diamond drill results indicate quartz veins are mineralized mainly with pyrite, tetrahedrite, sphalerite and argentite. Trenching exposed an electrum bearing quartz vein that pinches and swells over a 15 metre total length changing in character from a dry fracture to an electrum bearing ovoid pod of 10 centi- metres.

Electrum was encountered in only one quartz vein during the 1983 drill program when an 18 centimetre vein was intersected at 30 metres. A 0.5-metre section containing this vein assayed 50.09 grams per tonne gold and 47.31 grams per tonne silver. Another quartz vein intersected at 79 metres contained 2.0 per cent tetrahedrite and sphalerite and assayed 6.62 grams per tonne gold and 24 grams per tonne silver over 0.65 metre (Property File: Melnyk, W., 1983).