The Hydrogeochemistry of a Nickel-Mine Tailings Impoundment—Copper Cliff, Ontario
C.J. Coggans, D.W. Blowes, W.D. Robertson, J.L. Jambor, 1997. "The Hydrogeochemistry of a Nickel-Mine Tailings Impoundment—Copper Cliff, Ontario", The Environmental Geochemistry of Mineral Deposits: Part A: Processes, Techniques, and Health Issues Part B: Case Studies and Research Topics, G.S. Plumlee, M.J. Logsdon, L.F. Filipek
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The Copper Cliff tailings disposal area near the town of Copper Cliff, Ontario (Fig. 21.1) has been used continuously since 1936 and constitutes one of the largest mine disposal areas in the world. The six tailings impoundments within the disposal area cover 21 km2, accounting for more than 10% of all sulfide mine tailings in Canada (Feasby et al., 1991).
Approximately 35,000 t/day of ore from the Sudbury Igneous Complex, a fine-to-medium-grained noritic to gabbroic rock locally containing up to 60 wt% sulfides, is mined by INCO Ltd. and processed at the Copper Cliff mill. Monoclinic and hexagonal pyrrhotite (Fe1-xS), pentlandite ((Ni,Fe)9S8), chalcopyrite (CuFeS2), pyrite (FeS2), and cubanite (CuFe2S3) comprise the bulk of the sulfides. Minor concentrations of cobalite (CoAsS), nickelite (NiAs), galena (PbS), and millerite (NiS) are present (Hawley and Stanton, 1962; Naldrett, 1984). Approximately 95% of the copper and 80% of the nickel are recovered in the milling process, and the remainder is discharged to the impoundments with the bulk tailings (INCO Ltd. staff, personal commun., 1991).
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The Environmental Geochemistry of Mineral Deposits: Part A: Processes, Techniques, and Health Issues Part B: Case Studies and Research Topics
Environmental issues have become important, if not critical, factors in the success of proposed mining projects worldwide. In an ongoing and intense public debate about mining and its perceived environmental impacts, the mining industry points out that there are many examples of environmentally responsible mining currently being carried out (e.g., Todd and Struhsacker, 1997). The industry also emphasizes that the majority of mining-environmental problems facing society today are legacies from the past when environmental consequences of mining were poorly understood, not regulated, or viewed as secondary in importance to societal needs for the resources being extracted. On the other hand, environmental organizations (e.g., Mineral Policy Center, 1999) point to recent environmental problems, such as those stemming from open-pit gold mining at Summitville, Colorado, in the late 1980s (see Summitville summaries in Posey et al., 1995; Danielson and Alms, 1995; Williams, 1995; Plumlee, 1999), or those associated with a 1998 tailings dam collapse in Spain (van Geen and Chase, 1998), as an indication that environmental problems (whether accidental or resulting from inappropriate practices) can still occur in modern mining. Recent legislation imposing a moratorium on new mining in Wisconsin, and banning new mining in Montana using cyanide heap-leach extraction methods further underscore the seriousness of the debate and its implications for mineral resource extraction.
In this debate, one certainty exists: there will always be a need for mineral resources in developed and developing societies. Although recycling and substitution will help meet some of the worlds resource needs, mining will always be relied upon to meet the remaining needs. The challenge will be to continue to improve the ways in which mining is done so as to minimize its environmental effects.
The earth, engineering, and life sciences (which we group here under the term “earth-system sciences,” or ESS for short) provide an ample toolkit that can be drawn upon in the quest for environmentally friendly mineral resource development. The papers in this two-part volume provide many details on tools in the scientific toolkit, and how these tools can be used to better understand, anticipate, prevent, mitigate, and remediate the environmental effects of mining and mineral processing.
As with any toolkit, it is the professional’s responsibility to choose the tool(s) best suited to a specific job. By describing the tools now available, we do not mean to imply that all of these tools need even be considered at any given site, nor that