not_specified

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.

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.

A copy of this thesis is available at the EMR library – QE446.Y8 M67 1981.

The White River copper deposit, in upper Triassic Nikolai Greenstone of southwestern Yukon, is representative of the native copper-basalt association. Native copper and chalcocite are the association. Native copper and chalcocite are the most abundant ore minerals, but a substantial amount of bornite is known, as well as lesser amounts of chalcopyrite, pyrite, digenite, covellite, cuprite and native silver. These minerals are found in crosscutting fractures, amygdules, gas release tubes, small crackle zones, and as local disseminations in basalt; and although concentrated near the margins of a single glomeroporphyritic unit, are neither confined to that unit nor to a single zone within it. Two stages of copper mineralization are postulated: Stage I mineralization is thought to account for most of the native copper as a product of continental weathering of Nikolai basalts. Stage II mineralization is a much later event characterized by copper sulphides in crosscutting structures. Native copper and copper sulphides of Stage II appear to form a stable and primary product of a low grade (regional) metamorphism indicated by such minerals as chlorite, epidote, prehnite, pumpellyite, calcite analcite and apophyllite which have essentially the same mode of occurrence as primary copper minerals. Consequently, metamorphism (prehnite-pumpellyite facies) is interpreted to have been the mineralizing process. Whole-rock potassium-argon dating suggests an age no older than 120 million years for the metamorphic mineralizing event; hence, stage II mineralization post-dated host rock formation by at least 80 million years. It is probabe that many other copper occurrences in Nikolai Greenstone have formed in a similar manner. Also, it is likely that some of these mineralizing fluids could have moved higher in the stratigraphic sequence and precipitated copper minerals in other units.

not_specified