| Attenuation of aqueous metal transport at two natural acid rock drainage occurrences in the Yukon Territory, Canada |
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| 作者姓名： | Y.T. John Kwong |
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| 作者单位： | CANMET Mining and Mineral Sciences Laboratories, Ottawa, Canada |
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| 摘 要： | Naturally acidic drainage associated with pyritic black shale has been observed in many locations in the Yukon Territory. While not necessarily linked to known mineral deposits, most of these natural acid rock drainage occurrences show elevated dissolved concentrations of trace elements, especially zinc, nickel, copper, cadmium and arsenic. Based on field observations, microbial investigation, chemical analyses and geochemical modeling, the fate and transport of potentially deleterious elements at two natural acid drainage occurrences with slightly different settings are examined. The Macintosh Creek is a small, acidic stream （pH 2.98-3.40）, 2 km long, located in the Macmillan Pass area of east-central Yukon amidst known sedimentary exhalative massive sulfide mineralization but remains undisturbed by exploration activities. Its trace metal content is apparently derived from groundwater discharges, which gave as much as 5.0, 2.5, 0.7, 0.13 and 0.03 mg/L ofZn, Ni, Cu and As, respectively. Interaction and sorption reactions with algal mats, biofilms and iron oxyhydroxides appear to be the dominant mechanisms attenuating aqueous contaminant transport along the stream. Cryogenic precipitation further consolidates the ferricrete formation and reduces the mobility of the sorbed metals. The tributaries of the Engineering Creek along the Dempster Highway in northern Yukon drain through a series of dolomite, phyllite, argillite, limestone, black shale, sandstone and conglomerate with no known concentration of mineralization. In this area, the water chemistry fully reflects the local geology with acidic streams invariably associated with black shale occurrences. Groundwater seeps in the headwaters area of the km-180 Creek completely enclosed in black shale gave pH 3.0 and as much as 148, 39, 2.9 and 9.1 mg/L of Zn, Ni, Cu and As, respectively. Sorption with iron oxyhydroxide and organic matter appear to dominate the attenuation of contaminant transport along the stream. However, once entered into carbonate-dominated terrains, secondary carbonate minerals exercise additional geochemical control on the local water chemistry as a result of neutralization.
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| 关 键 词： | 酸性排水 金属污染 地球化学 堆积物 |
Attenuation of aqueous metal transport at two natural acid rock drainage occurrences in the Yukon Territory, Canada |
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| Y.T. John Kwong.Attenuation of aqueous metal transport at two natural acid rock drainage occurrences in the Yukon Territory, Canada[J].Chinese Journal of Geochemistry,2006,25(B08):229-230. |
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| Abstract: | |
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| Keywords: | black shale acid rock drainage metal contamination attenuation process geochemical modeling |
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