The Northern Lights orebody is part of the Silbak Premier Mine located 22 km north of Stewart, B.C.. The orebody is approximately 350 metres northwest of the main Premier orebody and lies at a deeper level. Mineralization on the Northern Light claims was discovered in 1927 and the orebody was brought into production in 1935. For an ex- panded capsule geology and bibliography refer to the Silbak Premier Mine (104B 054).
Located in the Intermontane Belt, the area, bounded on the west by the Coast Crystalline Complex and on the east by the Bowser Basin, is part of the volcanic arc assemblage of the Stikinia Terrane.
The deposit is hosted by Upper Triassic to Lower Jurassic Hazel- ton Group, Unuk River Formation metavolcanic rocks. The Hazelton Group is a northwest trending belt of folded andesitic to dacitic metavolcanic rocks containing a thick sequence of argillites and siltstones infolded along a synclinal axis.
The ore is hosted by massive andesite, andesite breccia and lap- illi tuff which are intruded by Early Jurassic Texas Creek plutonic suite dacitic porphyry dykes. The andesite, at least 750 metres thick, is unconformably overlain by volcaniclastic and epiclastic rocks. Potassium feldspar porphyry (historically known as the "Premier Porphyry") is spatially associated with the ore and this relationship is thought to indicate a Lower Jurassic mineralization age.
The Northern Lights orebody is situated in the hangingwall of the steeply northwest-dipping "Main" or "Northeast" zone. The dip of this zone varies from 60 degrees at surface to 30 degrees by the lowermost workings. The deposit is similar to the main Premier deposit as it also exhibits two distinct zone orientations. In the main orebody most production came from an area within about 500 metres of the intersection of these two zones. These trends are believed to represent structural controls to mineralization and emplacement of dacite porphyry intrusions. The ore is predominantly discordant but locally concordant with the moderately northwest- dipping andesite flows, breccias and dacite flows.
Hydrothermal alteration zones related to the mineralizing system are represented by a proximal silicification/quartz stockwork and potassium feldspar and/or sericite facies potassic alteration. Peripheral to mineralization is a propylitic alteration assemblage of carbonate, chlorite and pyrite. The variable intensity and type of alteration is partially controlled by fracture intensity and host lithology, and presumably, elevation in the hydrothermal system. The most characteristic feature of the andesite package is the pervasive carbonate, chlorite, and clay alteration around the deposit.
There are at least four styles of mineralization with textures ranging from stockwork and siliceous breccia to locally layered and massive sulphide-rich mineralization. Due to vertical mineral zonation, the Northern Lights orebody is more base metal rich with lower silver values than the Main deposit. Sulphide content varies, generally less than 5 per cent but can be as high as 75 per cent. Such ore diversity is an indication of the complex and episodic nature to ore deposition.
The base metal rich mineral assemblage consists of pyrite, sphalerite, galena, tetrahedrite, chalcopyrite, arsenopyrite, pyrr- hotite, electrum, and native silver. Gangue minerals are quartz, potassium feldspar, chlorite, carbonate and others.
A hybrid ore genesis model combining epigenetic vein and por- phyry copper characteristics compare well with the features observed.
Inferred ore reserves for the Northern Lights orebody in 1986 were 347,381 tonnes grading 4.04 grams per tonne gold and 39.42 grams per tonne silver, 1.5 per cent lead and 4.93 per cent zinc (George Cross Newsletter No. 18, Jan 27, 1986).
Production data is included in the Silbak Premier Mine pro- duction figures (104B 054).