Considerable research has been carried out into the reclamation and revegetation of disturbed lands in the Yukon, including operating and abandoned mines, and mineral exploration sites in the Yukon. Reclamation efforts on tailings have focused on methods to establish an initial vegetative cover on disturbed areas. Guidelines have been established by Kennedy (1993) and Hill et al. (1996) for the optimum mixtures of fertilizer and seeds (both agronomic and native varieties)¿. ¿.A relatively new and unique method of tailings processing and disposal that is being used at a few mines around the world is called dry stacking. This method of tailings disposal has the potential to provide many benefits to mining companies and affords numerous environment advantages that slurry deposits do not¿. ¿.The purpose of this proposed project was to research current practices in other jurisdictions and to examine the best approaches for encouraging vegetative establishment on dry stack tailings in norhtern environments, particularly for potential mine sites in the Yukon.

The Faro Down Valley Tailing Ponds contain residual quantity of minerals that have a total value of more than a billion dollars, however, only a portion of these minerals may be recoverable through research. A research proposal for the development of an economical reprocessing method for the recovery of this resource, which would create jobs and eliminate an environmental liability, was appoved for co-funding by the Government of Yukon, Department of Economic Development (Canada/Yukon Economic Development Agreement). This ambitious and diligent research program involved Canmet (Mineral Sciences Laboratories), Lakefield Research, Normet and Curragh Inc. The laboratory test results from the initial research programs are very encouraging with the production of a marketable bulk concentrate of 50% lead plus zinc metal content at a zinc metal recovery of 58%. There is considerable confidence in the Faro Down Valley Tailings reprocessing approach because of the mettalurgical results attained, the implementation of proven new technology equipment, the use of current reagents and the availability of the Faro Mill (low capital requirement) when the known, economic reserves are depleted.

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In July 2009 we re-visited the re-vegetation experiments, which had been set up on tailings in the period 2003-2006. The three experimental sites are at Mount Skukum, United Keno and Wellgreen. The experiments consisted of either seeding the tailings with various populations of the tufted hair grass and/ or with stratified (cold temperature treated) seed of the shrub soapberry, or making transplants of the same two species. The treatments included the addition of compost from the City of Whitehorse, addition of fertilizer as 7:7:7 pellets, addition of organic matter as sheep manure, peat or woody debris from on site and, in the case of Wellgreen, a lime addition to overcome the strong acidity. The results are striking and illustrated in the Plates 1-15. Data of performance and flowering success are shown in the Tables, as are chemical analytical data in the Figures and Tables. Plots set up in 2003 provide a nucleus for effective re-vegetation, having survived for 6 years. The success of the seedings and transplants at Mount Skukum and United Keno was good, while that at Wellgreen was very poor. Wellgreen has suffered flooding with washing out of plots and washing out of the neutralizing lime. Nevertheless, in compost additions plots at Wellgreen, set up in 2005 and 2006, a small amount of re-vegetation and survival has occurred, especially in the wetter areas near the tailings pond.

Placer mining occurs extensively in parts of the Yukon, denuding riparian zones and lining valley bottoms with mine tailings. Revegetation of tailings was examined at two placer mines near Mayo to determine the influence of environmental variables on the speed and direction of the natural process. Vegetation species density and frequency on various substrates were compared with: age, slope and aspect of the site, and pH, particle size distribution, moisture content and organic content of the soill. In central Yukon, tailings are first colonized by ruderal (weedy pioneer) species such as fireweed and members of the Compositae (dandelion) family. These are replaced by willow-dominated communities after nine years. Willow communities support many species characteristic of the adjacent undistrubed black spruce forest, suggesting that the placer succession is similar to that of riverbank environments in interior Alaska. Revegetation of the tailings proceeds at the same rate for the first twelve years as does that following natural disturbance. Of the environmental factors examined, only age and slope were, statistically, associated with rate of revegetation. Both the percent cover and the number of species at a site were inversely associated with slope, suggesting that reduction of slope angle enhances vegetation regeneration.

Whitehorse Copper Mine, within the city limits of Whitehorse, produced about 10 million tons of fine-grained calc-silicate tailings before its closure in 1982. The tailings, now desiccated, do not support plants although some areas have been undisturbed for more than 20 years. Barren tailings have high pH and electrical conductivity (E.C.) but are otherwise non-toxic. The minimum requirements for sustainable plant growth are under study in a pilot project in which freely available compost from various sources was mixed with the uppermost tailings as a proto-soil. Six plots were initially treated with one dose of chemical fertilizer, regularly irrigated and protected from wind. Planted Yukon native grasses germinated and both transplanted trees and seeds in the compost survived. Grass growth was measured after 2 growing seasons and is directly related to the quantity and quality of the compost tilled into the upper 10 centimetres of the tailings. Soil texture, moisture retention and organic nutrients improved. Similar abandoned sites could benefit from the addition of readily available compost and the use of locally propagated seeds and native plants.

The Brown-McDade deposit was the first vein system discovered in the Mount Nansen camp and has produced approximately 34,000 ounces (1058 kg) of gold and 131,000 ounces (4,075 kg) of silver from 225,000 metric tonnes of ore since production began in November, 1996. Production rates have varied since the mill start-up but the carbon-in-leach (CIL) plant is currently operating near capacity at 700 metric tonnes per day. Mining at the Brown-McDade open pit has exposed two separate and distinct deposit types. The first type is gold-silver vein mineralization hosted by a massive feldspar porphyry dyke. These fine-grained quartz-sulphide veins and vein breccia are enclosed by silicified and/or intensely clay-altered brecciated feldspar porphyry. The feldspar porphyry dyke has intruded along an igneous-metamorphic contact that has been mined over a strike length of 50 m in the southern portion of the pit. The second deposit type that occurs at the north end of the pit consists of a siliceous, sulphide-rich breccia in a pipe-like structure hosted by metamorphosed carbonate and clastic rocks of the Nasina Assemblage. The pipe is elongate in plan with a high-grade core approximately 15 m wide and 25 m long surrounded by a low-grade envelope consisting of quartz-sulphide stringers in a silicified breccia. The deposits are separated by a northeast-striking fault which truncates and offsets the main vein-dyke mineralization. The ore is composed of fine-grained quartz and sulphides in narrow veins or as matrix to a breccia of silicified and pyritized wall rock fragments. Unoxidized ore contains dark grey silica and pyrite, arsenopyrite, sphalerite, galena, sulphosalts, bornite, stibnite and chalcopyrite. Gold is genetically related to the pyrite phase of the mineralization and occurs as 5 to 50 micron-sized inclusions in pyrite grains. Oxidation of sulphide minerals extends to depths of up to 70 m and a large portion of the gold grains have been exposed by oxidation of the sulphides and post-depositional cataclastic fractures in the pyrite. The silver mineralogy is not as well understood but appears to be related to the base metal sulphide mineralization.

This study investigated background levels and uptake rates of organophilic metals, particularly selenium, in ten streams draining portions of the Yukon-Tanana Terrane and Cassiar Platform between Ross River and Watson Lake, Yukon. The study area is suspected to have elevated background metals concentrations and is of interest for mineral exploration and development due to high mineralization. Information on natural metals levels is lacking for this region and for the Yukon in general. Water, sediments, benthic invertebrates and fish (slimy sculpin; Cottus cognatus) were sampled and analyzed for metals concentrations. Benthic invertebrates were identified to genus and percent composition of each species in each stream was calculated. The lack of anthropogenic activity in the area indicates that selenium concentrations found in all sample media and natural, background concentrations. Of all the sample media, concentrations of selenium were highest in sediment; however, sediment selenium concentrations were found to be in a range similar to levels documented at the Kudz Ze Kayah and Viceroy Brewery Creek mines in other regions of the Yukon. Selenium concentrations in water generally exceeded CCME guidelines, but also fell within a range similar to the Kudz Ze Kayah and Viceroy Brewery Creek mines. These findings with respect to selenium levels in water and stream sediments highlight the importance of developing site-specific selenium guidelines for management of aquatic systems. The rate of uptake of selenium in benthic invertebrate and fish tissues was greater than that of the other organophilic metals investigated. Selenium concentrations were generally higher in benthic invertebrates than in fish, likely owing to the detritus-feeding and bottom-dwelling life history of these invertebrates. Weak positive trends were noted in the relationship between selenium concentrations in fish and benthic invertebrates, and between fish and the water column. A significant positive relationship was noted between selenium concentrations in fish and stream sediments. These findings are consistent with past studies documenting dietary sources as the most common uptake pathways for selenium, with water comprising a secondary source. Examination of benthic invertebrate community composition revealed commonly abundant species and species typical of fast-flowing streams with high water quality, which is characteristic of the streams in the study area. The findings of this study provide valuable baseline information on background concentrations of metals, particularly selenium, as well as documentation of benthic invertebrate community composition, in an aquatic system that may experience resource development in the future.

In February 2000, Yukon Government Mineral Resources Branch convened a panel of industry geologists to estimate the likelihood of new discoveries in Cassiar Terrane and eastern Yukon-Tanana Terrane. The estimates were processed in a mineral deposit simulator. The simulated tonnage of metal for each tract (approximately 1000 km² of coherent geology) was converted to a dollar value, which in turn was used to rank the tracts relative to each other, from lowest to highest mineral potential. Separate runs of the simulator for significant deposit models were completed to produce model specific maps.