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TitleDownstream changes in antimony and arsenic speciation in sediments at a mesothermal gold deposit in British Columbia, Canada
AuthorBeauchemin, SORCID logo; Kwong, Y T J; Desbarats, A JORCID logo; MacKinnon, T; Percival, J BORCID logo; Parsons, M BORCID logo; Pandya, K
SourceApplied Geochemistry vol. 27, no. 10, 2012 p. 1953-1965,
Alt SeriesNatural Resources Canada, Contribution Series 20182617
PublisherElsevier BV
Mediapaper; on-line; digital
File formatpdf
ProvinceBritish Columbia
Released2012 10 01
AbstractThis study investigates Sb speciation in sediments along the drainage of the Upper Peter adit at the Bralorne Au mine in southern British Columbia, Canada, and compares the behavior of Sb with that of As. The Upper Peter mineralization consists of native Au in quartz-carbonate veins with 1wt.% sulfides dominated by pyrite and arsenopyrite although stibnite, the primary Sb-bearing sulfide mineral, can be locally significant. Dissolved Sb concentrations can reach up to 349?gL -1 in the mine pool. Sediments were collected for detailed geochemical and mineralogical characterization at locations along the 350-m flow path, which includes a 100-m shallow channel within the adit, a sediment settling pond about 45m beyond the adit portal and an open wetland another 120m farther downstream. From the mine pool to the wetland outlet, dissolved Sb in the drainage drops from 199?gL -1 to below the detection limit due to the combined effect of dilution and removal from solution. Speciation analyses using X-ray absorption near-edge structure (XANES) spectroscopy indicate that Sb(III)-S accounts for around 70% of total Sb in the sediments in the main pool at the far end of the adit. At a short distance (24m) downstream of the main adit pool, however, Sb(III)-O and Sb(V)-O species represent ?50% of total Sb in the bulk sediments, indicating significant oxidation of the primary sulfides inside the adit. Although Sb appears largely oxidized in the bulk samples collected near the portal, Sb(III)-S species are nevertheless present in the <53-?m fraction, suggesting a higher oxidation rate for stibnite in the coarser grains, possibly due to galvanic interaction with pyrite. Secondary Sb species released from the sulfide oxidation are most likely sorbed/co-precipitated with Fe-, Mn-, and Al-oxyhydroxides along the flow channel in the adit and in the sediment settling pond, with the Fe phase being the dominant sink for Sb. © 2012.

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