| Title | Speciation, transport, and fate of arsenic in the Seal Harbour gold district, Nova Scotia, Canada |
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| Author | Parsons, M B ;
Hall, G E M; Daniels, C; Corriveau, M C; Jamieson, H E; Smith, P K; Goodwin, T A; Percival, J B; Vaive, J E; Pelchat, P |
| Source | Geological Society of America, Abstracts With Programs vol. 38, no. 7, 2006 p. 321 |
| Links | Online - En ligne
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| Image |  |
| Year | 2006 |
| Alt Series | Earth Sciences Sector, Contribution Series 20060144 |
| Publisher | The Geological Society of America (GSA) |
| Meeting | 2006 Geological Society of America Annual Meeting and Exposition; Philadelphia, PA; US; October 22-25, 2006 |
| Document | serial |
| Lang. | English |
| Media | paper; CD-ROM |
| File format | htm |
| Province | Nova Scotia |
| NTS | 11F/04 |
| Area | Seal Harbour |
| Lat/Long WENS | -62.0000 -61.5000 45.2500 45.0000 |
| Subjects | tailings; tailings analyses; tailings geochemistry; arsenopyrite; gold; mineral deposits; mining; mercury; stream water geochemistry; sediment geochemistry; arsenic; arsenic geochemistry; heavy metals
contamination; biota |
| Program | Geoscience
for Oceans Management |
| Released | 2006 01 01 |
| Abstract | Arsenopyrite occurs naturally in Cambro-Ordovician lode gold deposits in Nova Scotia, and is present at high concentrations in the tailings at past-producing mines. This study is a multi-disciplinary
investigation of the dispersion, speciation and fate of metal(loid)s in the environment surrounding the Upper and Lower Seal Harbour mining districts. Early gold recovery efforts (1893-1927) employed stamp mills and Hg amalgamation, whereas later
operations (1936-1941) used mainly cyanidation. More than 500,000 tonnes of tailings from these mills were slurried into local watercourses, and have been transported more than 2 km to the ocean where they form an intertidal tailings flat. From 2003
to 2005, samples of tailings, soil, till, rock, sediment, water, and biota were collected throughout the Seal Harbour districts. Chemical analyses of 200 tailings and stream sediment samples show high concentrations of both As (39 ppm to 31 wt.%;
mean 1 wt.%) and Hg (12 ppb to 120 ppm; mean 3 ppm). The speciation of As in these samples was examined using electron microprobe, conventional and synchrotron-based X-ray diffraction, X-ray absorption near edge structure, and sequential extractions.
In addition to As-bearing sulfides, As is hosted by a variety of secondary phases such as scorodite (FeAsO4·2H2O), amorphous Fe arsenates, Ca-Fe arsenates, and Fe oxyhydroxides. Dissolved As concentrations in surface waters and tailings pore waters
indicate that the tailings continue to release significant quantities of As. In the Summer, dissolved As concentrations in surface waters range from 20 to 6200 ppb, as compared to background values of <2 ppb. In the Spring and Fall, dissolved As
concentrations are generally 2-3 times lower than in the Summer. Measurements of As(III) and As(V) show that As(V) constitutes more than 90% of the dissolved As in most surface waters. Analyses of sediments and water in the adjacent marine
environment indicate that Seal Harbour is an effective trap for tailings, and As-enriched floc formed upon mixing of river water. Biological sampling by project partners has demonstrated that both As and Hg have bioaccumulated to various degrees in
terrestrial and marine biota, including eels, clams, and mussels. A bivalve shellfish closure is now in effect for Seal Harbour to prevent harvesting of As-contaminated clams. |
| GEOSCAN ID | 222593 |
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