The Red Dog zinc/lead deposit in northwest Alaska is the second largest zinc deposit ever discovered. Being developed by Cominco Alaska with startup scheduled for early 1990, it will ultimately be the largest zinc mine in the Western World.
Red Dog was discovered by a local bush pilot, Bob Baker, in 1968. The U.S. Geological Survey assessed the find, but the Red Dog site had been withdrawn from staking by the provisions in the Alaska Native Claims Settlement Act of 1971 (ANCSA). The deposit was selected, under the terms of ANSCA, by the NANA Regional Corporation, one of 13 native corporations established by the Act. This selection was confirmed by Congress in the 1980 Alaska National Interest Lands Conservation Act.
In 1982, Cominco and NANA reached an agreement which has led to the development of the mine. Under its terms, Cominco leases the property from NANA, develops and operates the mine, and markets the concentrate produced. In return, NANA receives royalties, and after capital recovery, participates in the net proceeds from the Operation.
The Alaska State Government is also playing a role in the development of the mine. Under the auspices of the Alaska Industrial Development Authority (AIDA), the State will construct, own, and operate the DeLong Mountains Regional Transportation System. This consists of a 52 mile road from the Minesite to the Chukchi Sea and associated port facilities necessary to store and ship the annual concentrate production and receive the mine fuel and supplies. For using this transportation system, Cominco will pay an annual toll fee, which over the anticipated 50 year life of the operation will provide a 6.5% return to the State of Alaska.
Cominco’s Board of Directors approved the Project in late 1986, and construction of the road commenced during the summer of 1987. Construction at the Millsite and initial stripping of the orebody is expected to start in February 1988. The Project is currently geared to a startup in the first quarter of 1990.
Project Setting
The project site is approximately 1,000 km (600 mi) northwest of Anchorage, 84 km (52 mi) from tidewater on the Chukchi Sea and 192 km (120 mi) north of the Arctic Circle (see Figure 1). The countryside consists of low rolling hills which lead into mountains both north and east of the deposit. The vegetation is typical tundra mat, and the site is in an area of permafrost. However, the permafrost is relatively warm and some areas, for example creek bottoms and the site of the main waste dump, have been found to be thawed.
Red Dog is a stratiform zinc/lead/silver deposit with associated barite. Mineralization occurs in two areas at the Main Deposit and at the Hilltop Deposit. The Hilltop Deposit, located one-half mile to the south of the main deposit, has not yet been adequately defined and could pose problems in the treatment process .
The main deposit is a flat-lying, elongated lens of mineralization with a maximum thickness of 150 m (500 ft) and a length of more than i,300 m (4,400 ft). Width varies from 60 m (200 ft) in the north to 430 m (1,400 ft) in the central and southern portions. Overburden is limited to a thin mantle of weathered ore and waste rock except for two ridgetop locations where up to 60 m (200 ft.) of barren shales and chert is encountered.
The Red Dog deposit is a package of inter- stacked lenses composed of differing portions of sulfides, quartz, and barite.
Sulfides in decreasing order of abundance are sphalerite, pyrite, marcasite, and galena. Silver is associated with both the zinc and lead sulfides and significant amounts of cadmium occur in the sphalerite. Overall, iron content is low to moderate. Sulfides are generally fine-grained. Coarse-grained sphalerite occurs principally in footwall and peripheral veins. The dominant gangue constituents are quartz, barite, minor shale, and calcite.
Developing Red Dog is a challenging venture. Its location in the Arctic, with inherent environmental concerns, poses awesome logistical difficulties. It is a huge project requiring a large capital outlay, securing of numerous permits, and passage of Federal and State legislation. The partnership between Cominco and NANA is unique in that it is the first major resource development in Alaska in which a native corporation has had direct participation.
To be successful, Cominco will have to apply all the knowledge gained in 50 years of mine development in the north and Arctic, plus adaptations of valuable lessons learned in developing the oil reserves in the Alaskan and Canadian Arctic.
However, once in operation, Red Dog will become a major player in the zinc industry, providing a basis for Cominco well into the next century, and providing much needed industry and employment to northwest Alaska.
