Copper Gold Silver Cobalt Zinc

The Hidden Creek (Anyox) mine, near Observatory Inlet and just west of Granby Bay, was a major copper producer between 1914 and 1936.

The area is underlain by the western margin of a 14.4 by 9.6 kilometre roof pendant within the Eocene Coast Plutonic Complex. Recent geochronology and fossil research by the Geological Survey of Canada have helped define the age of the pendant. These pendant rocks have been correlated with Lower to lower Middle Jurassic Hazelton Group rocks and overlying upper Middle to Upper Jurassic Bowser Lake Group sedimentary rocks (Geological Survey of Canada Open File 3453). The Hazelton rocks consist of variably chloritized pillowed and massive basalt with minor mafic tuffs. The overlying Bowser Lake sediments consist of siltstone and sandstone with minor chert and limestone. There are two observable phases of folding in the area, an initial north-northeast trending phase followed by a later east-northeast trending phase.

The Anyox deposit consists of eight distinct massive sulphide bodies, numbered 1 to 8, and a quartz vein stockwork containing disseminated sulphides. The underlying volcanics consist of tholeiitic pillow basalts and basaltic tuffs, with the frequency of tuff lenses and layers increasing upwards through the sequence. Chloritization, quartz veining and sulphide impregnation also increases upwards. A chert horizon, followed by a turbidite sequence of quartzofeldspathic silt and pelite metamorphosed to argillite, overlies the volcanics and massive sulphides.

The structure is dominated by an asymmetrical overturned anticline/syncline pair. The Number 1, 4, 5, 6, 7 and 8 orebodies occur along the volcanic/sediment contact, around the nose of the anticline which plunges north at 30 degrees. The Number 2 and 3 orebodies occur in volcanics, 30 to 100 metres west of the volcanic/sediment contact, on the west limb of a north plunging asymmetrical fold. A north striking, steeply east-dipping fault separates the Number 2 and 3 orebodies, which formed a single body before being displaced 90 metres vertically and 60 metres horizontally. The Number 2 and 3 orebodies strike north and dip steeply to the east, and the Number 1 body strikes north to northeast and dips 50 to 90 degrees to the west. The dimensions of the massive sulphide bodies range from 500 by 400 by 76 metres for the Number 1 deposit to 150 by 100 by 21 metres for the Number 6 deposit.

Two types of massive sulphide bodies are distinguished at Anyox. The more common type, which includes the Number 1, 4, 5, 6, 7 and 8 orebodies, consists of stratiform tabular to elongate massive sulphide orebodies interbedded with cherty metasediments on the volcanic/sediment contact. Mineralization consists primarily of pyrite and lesser pyrrhotite with chalcopyrite and sphalerite occurring as fine disseminations or as massive layers and lenses within the pyrite and pyrrhotite. The sulphides form massive layers up to 75 metres thick. Gangue minerals consist of quartz, chlorite, actinolite, tremolite, calcite, biotite and sericite.

The Number 2 and 3 orebodies characterize the second type which consists of massive stratabound layers and lenses of sulphides in basaltic tuff. The tuff has been altered to chlorite or chlorite actinolite schist. Mineralization consists of massive pyrrhotite, variable amounts of chalcopyrite and minor pyrite. The mineralization forms layers, lenses and disseminations in the tuff. Gangue minerals consist of quartz, chlorite, actinolite, hornblende, epidote and albite.

West of the Number 2 and 3 deposits, a stockwork of epigenetic quartz veins forms a low grade, unmined and poorly defined copper orebody. Mineralization consists of pyrrhotite, chalcopyrite, minor pyrite and trace sphalerite occurring as disseminations and blebs in chloritized metabasalt and quartz veins.

Between 1914 and 1936, 21,725,524 tonnes of copper ore were produced from the Number 1 to 6 bodies. The average grade was 1.4 per cent copper, 0.17 gram per tonne gold and 9.5 grams per tonne silver.

The North Hidden Creek showing, located 300 metres north of the mine, consists of two massive sulphide intersections obtained from 1982 drilling. The intersections occur above the basalt/argillite contact in hangingwall sedimentary rock units. A 6.1-metre intersection in Hole 82-9 assayed 2.5 per cent copper, 0.5 per cent zinc, 1.7 grams per tonne gold and 99.4 grams per tonne silver (Report by Taiga Consultants Ltd., 1992).

In 1983, Wright Engineers Limited estimated remaining ore reserves at Hidden Creek to be 77 million tonnes grading 0.55 per cent copper equivalent. In the same year, Cominco computerized the data and calculated a potential mineralized ore reserve, to a depth of 60 metres, of 45,360,000 tonnes grading 0.60 per cent copper, with a cutoff of 0.2 per cent copper (Report by Taiga Consultants Ltd., 1992).

In 1988, Glanville Management Ltd. concluded that open pit reserves present were 10.9 to 13.6 million tonnes, grading 0.70 to 0.75 per cent copper, with gold and zinc grades (Report by Taiga Consultants Ltd., 1992). This report and Assessment Report 23528 have a good summary and history of exploration in the Anyox area.

In 1992, Beacon Hill Consultants Ltd. outlined an indicated open pit reserve of 24,221,840 tonnes grading 1.08 per cent copper, 0.17 gram per tonne gold and 10.3 grams per tonne silver (George Cross News Letter No. 21 (February 1), 1993 and Report by Taiga Consultants Ltd., 1992).