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TitleForm and distribution of gold mobilized into surface waters and sediments from a gossan tailings pile, Murray Brook massive sulphide deposit, New Brunswick, Canada
AuthorLeybourne, M I; Goodfellow, W D; Boyle, D R; Hall, G E M
SourceApplied Geochemistry vol. 15, issue 5, 2000 p. 629-646,
LinksAbstract - Résumé
Alt SeriesGeological Survey of Canada, Contribution Series 1999076
PublisherElsevier BV
Mediapaper; on-line; digital
File formatpdf
ProvinceNew Brunswick
AreaMurray Brook
Lat/Long WENS -66.5000 -66.2500 47.7500 47.5000
Subjectseconomic geology; geochemistry; hydrogeology; gold; mineralization; sulphides; sulphide deposits; stream sediment geochemistry; tailings; tailings geochemistry; groundwater flow; supergene deposits; solubilities; Murray Brook Massive Sulphide Deposit; massive sulphide deposits
Illustrationslocation maps; geochemical sketch maps; cross-sections, stratigraphic; ternary diagrams; tables; graphs; geochemical plots; formulae
ProgramCanada-New Brunswick Exploration Science and Technology (EXTECH II) Initiative, 1994-1999, Bathurst Mining Camp
AbstractStream waters and sediments draining a gossan tailings pile at the Murray Brook massive sulphide deposit were collected to investigate Au mobility. Weathering of the massive sulphides at Murray Brook during the Late Tertiary period resulted in the concentration of Au in the gossan cap overlying the supergene Cu and unoxidized massive sulphide zones of the deposit. The gossan was mined between 1989 and 1992, and Au and Ag were extracted using a cyanide vat leach process. Although stream sediments prior to mining had Au < 5 ppb (the detection limit), sediments collected in 1997 had Au contents ranging up to 256 ppm with values up to 6 ppm more than 3 km downstream from the deposit. Dissolved Au contents were similarly anomalous, up to 19 mg/L and in excess of 3 mg/L 3 km downstream. The elevated Au contents in the waters and sediments are interpreted to re¯ect complexation of Au (as Au(CN)2 ÿ ) by cyanide hosted within the gossan tailings pile. Precipitation recharges through the tailings pile with groundwater ¯ow exiting to Gossan Creek. Degradation of cyanide along the ¯ow path and within Gossan Creek allows colloidal Au to form via reduction of Au(I) by Fe2+, consistent with SEM observations of Au as <1 mm subrounded particles. In the surface waters, the majority of the Au must be in a form <0.45 mm in size to account for the similarity in Au contents between the <0.45 mm and un®ltered samples. The very elevated stream sediment Au values close to the headwaters of Gossan Creek near the tailings indicate that upon exiting to the surface environment, Au(CN)2 ÿ complexes are rapidly destroyed and Au removed from solution. However, the high Au<0.004 mm/Autotal in the headwaters and the extended Au dispersion in Gossan Creek waters and sediments suggest that Au(CN)2 ÿ complexes persist for the full length of Gossan Creek. The decrease in aqueous Au which is less than 0.004 mm indicates that Au is converted from a complexed form to a colloidal form with increasing distance downstream, consistent with dissolved NO3 ÿ contents which decrease from 5210 mg/L near the headwaters to 1350 mg/L at the lower end of the stream.