Overview & Geology

Geography

The Myra Falls Operation (MFO) is located 95 kilometres by road from Campbell River, at the south end of Buttle Lake within the Strathcona provincial park in the central mountainous area of Vancouver Island. It hosts Vancouver Island’s highest mountain peaks and Canada’s tallest water falls. Strathcona Park is entirely within the Vancouver Island Coastal Range of the Vancouver Island Mountains; the Alberni Basin and the Estevan Coastal Plain are two lowland areas, one along the west coast and the other inland of Alberni Inlet, which complete the physiographic components of the Vancouver Island Mountains. Strathcona Park lies on the backbone ridges of the Vancouver Island Coastal Range. Numerous peaks exceed 1,500 metres in elevation. Buttle Lake lies almost in the centre of the park, with a mean water level of 221 metres above sea level holding the lowest inland elevation. The topographic relief at Myra Falls is over 380 meters above sea level in the valley and 1,300 meters to the highest ridge top.

Geology

The Myra Falls polymetallic deposit is comprised of complex series of Volcanic Hosted Massive Sulphide (VHMS) orebodies. The principal sulphide minerals are sphalerite, pyrite and chalcopyrite with minor galena, bornite, and tennantite. There is strong geological continuity of the orebodies although there is significant variation in mineralogy and grades along strike, with vertical zonation and structural displacement. VHMS deposits on Vancouver Island, including those at Myra Falls, are hosted by ancient island arc systems of the Paleozoic Sicker Group (Hoy, 1991). The Paleozoic Sicker Group is considered part of the allochthonous Wrangellia Terrane, which is a portion of the Insular Belt of the Canadian Cordillera.

The Wrangellia Terrane has three major volcano-sedimentary cycles and one intrusive event which can be traced for 2,000 km from the southern tip of Vancouver Island northward to south-central Alaska (Jones et. al, 1977). At Myra Falls, the oldest volcanic cycle is the Devonian to Mississippian Sicker Group of volcanic rocks which are conformably overlain by limestones of the Permian Buttle Lake Formation. The second volcanic cycle is the Vancouver Group comprised of the Karmutsen Triassic Formation tholeiitic volcanics. This unit is overlain by limestones of the Quatsino Formation.