The B.C. Silver ore bodies of the British Silbak Premier Mine are located north of the main deposit (104B 054), 22 kilometres north of Stewart, B.C. These ore bodies are the northeast extension of the "Northeast or Main" ore zone of the Premier deposit. The property was originally owned by B.C. Silver Mines Ltd. who intersected ore in 1922, about 475 metres east of the main deposit. In 1935 when the property was amalgamated along with the Sebakwe property into British Silbak Premier Mines Ltd., there was a total length of four miles of underground workings. For a more extensive capsule geology and bibliography refer to the Silbak Premier mine.
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 in Upper Triassic to Lower Jurassic andesitic to dacitic volcanic rocks, correlated with the Hazelton Group, Unuk River Formation. The Hazelton Group is a northwest trending belt of folded metavolcanic rocks containing a thick sequence of argillites and siltstones infolded along a synclinal axis.
The ore is hosted by andesite flows, breccia and lapilli tuff, intruded by the Early Jurassic Texas Creek plutonic suite dacitic porphyry dikes. Potassium feldspar porphyry (historically known as the "Premier Porphyry") is spatially associated with the ore; this relationship is thought to indicate a Lower Jurassic mineralization age.
The B.C. Silver ore bodies occur as the northeast extension of the steeply northwest-dipping, "Main" or "Northeast" zone of the Premier deposit (104B 054). The mineralization in this zone dips at 60 degrees near surface and flattens to 30 degrees by the lowermost workings. This trend is believed to represent structural control on 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. The B.C. Silver orebodies appear to be offset in several planes with by up to 35 metres.
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.
Ore minerals include pyrite, sphalerite, galena, with minor tetrahedrite, chalcopyrite, arsenopyrite and local pyrrhotite. Bonanza ore contains native gold, electrum, pyrargyrite, polybasite, argentite and native silver. Gangue minerals are quartz, potassium feldspar, chlorite, carbonates and others.
Sulphide content varies, generally less than 5 per cent but can be as high as 75 per cent. Textures range from stockwork and siliceous breccia to local layered to massive sulphide-rich mineralization. Such ore diversity is an indication of the complex and episodic nature to ore deposition. A hybrid ore genesis model combining epigenetic vein and porphyry copper characteristics compare well with the features observed.
By 1935 B.C. Silver Mines had shipped 920 tonnes of ore producing 68,560 grams of gold and 2,742,400 grams of silver (Geological Survey of Canada Memoir 175).
Post 1935 production is included with production figures for the Silbak Premier Mine (104B 054).
In 2014, a total of 14 diamond-drill holes were completed in the BC Silver zone. In the BC Silver zone, 8 out of the total 14 drillholes were abandoned or shortened either due to the presence of the overlying waste dump or gravelly clay faults. All holes collared into a Latite/Dacite flow layer, which is the extrusive equivalence of the Premier Porphyry, of a thickness of 30 to 100 metres. The gentle to moderate west dipping Latite Flow is characterized with fine to medium grained foliated plagioclase phenocrysts and sporadic plagioclase and feldspar megacrysts and with local hematite alteration. A layer of the Betty Creek Formation sits right below and dips at the same orientation as the Latite flow with a thickness of 10 to 30 metres. The mineralized zone dips at the same orientation as the Latite flow and the Betty Creek Formation. The mineralized zone is about 3-12 metres in thickness characterized with 3 to 7 per cent pyrite and 1 to 3 per cent sphalerite/galena and local trace to 1 percent chalcopyrite. The QSP (quartz-sericite-pyrite) alteration halo of the breccia zone ranges from 30 to 50 metres in thickness characterized with stockwork and relatively lower base metals content than the breccia zone. In general, the BC Silver and the Sebakwe (104B 153) have higher silver:gold ratios relative to the Northern Lights (104B 053), the Premier West, and the Premier Main zones.
Hole P146-09 intersected 47.18 metres (from 185.82 to 233.00 metres) grading 1.12 grams per tonne gold and 9.7 grams per tonne silver, including 10.21 metres (from 190.00 200.21 metres) grading 3.27 grams per tonne gold and 18.0 grams per tonne silver (Assessment Report 35410, pages 63-64).
Ascot Resources took control of the Premier-Big Missouri project in 2007 and started an intensive exploration program and collation of all work toward a GIS database of 4,453 historic holes of the Premier Mine area which comprises six major zones: Premier (including the Premier West zone the Premier Main zone), Northern Lights zone, BC Silver zone, Sebakwe zone, and Hope and Power zones. Ascot was able to demonstrate the continuity and the linkage between all six zones with targets still open for exploration in multiple directions.
Refer to Silbak Premier (104B 054) for a broader discussion of geological information and more complete bibliography of the Premier Mine area.
