Mining activity at the Whitehorse Copper Mine has resulted in a disturbed land area of approximately 800 acres. Within this area there are about 53 acres with active slope instability and subsidence associated with the mine and underground workings. The mine is located within the city limits of Whitehorse, about six miles from the city centre. Although the mine has been decommissioned to a level acceptable to the mine inspector, there is still some concern for public safety. In addition, the current decommissioning plan is expected to result in the permanent loss of useful land from within the city limits. This report presents an assessment of the site conditions and options for reclamation to address these concerns.

This report on the Whitehorse Copper Belt is written by a geologist who was actively involved in mining and exploration in the district during the decade of the seventies. It includes a review of earlier data and compiles recent work, mining practice, geological concepts and constraints and problems in development and mining. Earlier reports on the district by McConnell and Kindle emphsized geology; this report concentrates on mining and development. The report was written when mining in the district was at its peak; it will be useful to those contemplating future development in the Copper Belt and for comparing the district to others. Mining in the Copper Belt may cease soon and the report was solicited by D.I.A.N.D. from Whitehorse Copper Mines as a record of mining practice and geological concepts.

The Whitehorse Copper Belt is a northwest-trending chain of copper-bearing skarn deposits, located four kilometres west of the city of Whitehorse (NTS 105 D). The belt extends parallel to the Alaska Highway for thirty kilometres, from the Crestview subdivision to the junction of the Alaska Highway and the South Klondike Highway. From the time Jack McIntyre staked the Copper King in 1898, the belt has been vigorously prospected and mined for its valuable copper, gold and silver metals.

Geology of the Whitehorse Copper Belt (NTS 105 D/11), southern Yukon. A compilation including a 1:25 000-scale geological map with marginal notes on bedrock geology, mineral occurrences, mineral deposits and grades of some mineral deposits.

In the first three decades of this century, $2,712,000 worth of copper ore came out of the copper belt (Johnston, 1975). The mines were only active, however, when copper prices were high. Ultimately, the drop in copper prices after the first World War, the discontinuous nature of the copper deposits, and the high cost of transport brought an end to production in the copper belt for half a century. In the 1960s and 1970s, modern mining technology made it profitable to mine copper ore on a large scale, an undertaking that had proven uneconomical in the early days. Nonetheless, New Imperial Mines Ltd., later Whitehorse Copper Mines Ltd., had much in common with those early mines. Transportation costs were still high, the extent of mining development depended on outside capital investment and world copper prices, and there was still a close connection with the nearby community of Whitehorse. A companion paper discusses the geology of the area as well as the historic and contemporary mining technology used in the copper mines. This document will address historic events and issues during 85 years of exploration, development and production in the copper belt (NTS 105 D).

This publication is a field guide to the geology and mining history of the Whitehorse Copper Belt. It is designed to assist Whitehorse residents and visitors in exploring this fascinating area. Sheet 1 is a geological map with a list of suggested stops, while sheet 2 provides specific descriptions of many mineral occurrences. Stops are numbered roughly from north to south on this map, and are grouped according to their geographic location and access routes on sheet 2.

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This project was undertaken to evaluate the potential to economically recover additional metal values from the 4.6 million tons of Keno Hill flotation tailings which grades 3-4 oz/t silver, 0.8% lead and 0.9% zinc. The study determined that the higher grade portion of the tailing, containing some 1.0 million tons at 5.35 oz/t Ag, responds well to cyanide heap leaching with a silver recovery of 50-60%. The testing data suggests that heap leaching is economically feasible at the current silver price of $US5.50/ounce and a currency exchange rate of 1.35 in favour of the US dollar. The response to gravity and flotation concentration was poor.

Skarns in the Whitehorse Copper Belt occur in both dolomitic and calcareous carbonate rocks near contacts with the diorite contact phase of the Whitehorse Batholith. The skarns are mineralogically and compositionally similar to typical copper skarns. The bulk of sulphide mineralization is associated with retrograde alteration. Chalcopyrite and pyrite are preferentially associated with actinolite and chlorite, whereas bornite and chalcocite are preferentially associated with epidote and locally serpentine. The other important copper mineral, valleriite, is restricted to magnesian rocks and is commonly associated with phlogopite, serpentine, and chlorite. Overall, the Whitehorse system is copper-rich and sulphur-poor; iron sulphide minerals are not abundant. Significant amounts of gold and silver have been recovered from the Whitehorse skarns. Cu, Ag, and Au metal raiots of spot sample assays can be used to discriminate among the different Whitehorse skarns. Deposits formed from relatively pure limestone appear to have low precious metal ratios. Deposits formed from more magnesian protoliths appear to be silver-rich. Deposits with the highest gold ratios appear to have formed from mixed limestone-dolostone lithology.

URL: https://geoscience.data.qld.gov.au/dataset/cr000585 NINETY MILE COPPER MINE REPORT BY S R L SHEPHERD 7/1/1961