| Summary: | The Stirling Zn-Pb-Cu mine, located at Stirling in Richmond County, Cape Breton Island, was active between 1935 and 1938, and 1952 and 1956, when one million tons of ore were produced grading 6.21% Zn, 1.48% Pb, and 0.73% Cu. During the first period, 180 0001 of tailings were discharged directly into Strachans Brook, whereas in the 1950s the tailings, totalling 800 0001, were impounded. Since that time there has been ongoing erosion and downstream dispersion of tailings. The purpose of this study was to quantify this dispersion, to determine the effectiveness of neutralization of acid generation in the tailings, and to evaluate levels of downstream contamination. Downstream sediments in Strachans Brook have mean metal enrichments of 70x Zn, Pb and Cu, 35x Cd, As, and Ag, 20x Au, and lOx Mn, compared to upstream sediments. Close physical and geochemical similarities between tailings and downstream sediments indicate a severe level of downstream contamination. Runoff from the tailings is pH-neutral, strongly enriched in sulphate, Ca, Mg, Fe, Mn, Zn and Cu, and slightly enriched in Cd, As, Sb, Se, Co, Ni, V, and Cr. However, downstream water is less acidic than upstream water and is slightly enriched only in Ca, Mg, Mn, and Zn. Dispersion of metals in solution is minimized due to effective neutralization by dolomite of acid generation within the tailings, and its impact on the downstream environment is reduced by upstream dilution of the effluent from the tailings. RÉSUMÉ La mine de Zn-Pb-Cu Stirling située a Stirling comté de Richmond, dans File du Cap-Breton, a été en activite entre 1935 et 1938 puis entre 1952 et 1956. On y a produit un million de tonnes de minerai d'une teneur de 6,21 % de Zn, 1,48 % de Pb et 0,73 % de Cu. Au cours de la première période, 180 000 t de résidus ont été rejetées directement dans le ruisseau Strachans, alors que dans les années cinquante, on a accumulé une ...
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