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TitleMobilization of gold into lake sediments from acid and alkaline mineralized environments in the southern Canadian Shield: gold in lake sediments and natural waters
AuthorSchmitt, H R; Cameron, E M; Hall, G E M; Vaive, J
SourceJournal of Geochemical Exploration vol. 48, 1993 p. 329-358,
Alt SeriesGeological Survey of Canada, Contribution Series 55590
PublisherElsevier BV
Mediapaper; on-line; digital
File formatpdf
ProvinceOntario; Manitoba; Saskatchewan
NTS31F/02; 64C/10; 64C/11; 73P/07
AreaPap Lake; Foster Lake; Napier Lake; Canadian Shield
Lat/Long WENS-105.0000 -76.0000 56.7500 45.0000
Subjectsgeochemistry; water geochemistry; lake sediment geochemistry; gold geochemistry; mineralization; stream sediment geochemistry; Aphebian; acidity; indicator elements; Precambrian
Illustrationssketch maps; photomicrographs; analyses
ProgramCanada-Ontario Mineral Development Agreement, 1985-1990
ProgramCanada-Ontario Mineral Development Agreement, 1985-1990
AbstractTo be an effective indicator of mineralization in lake sediment surveys within the Canadian Shield, it is desirable that an element migrate in solution or adsorbed on suspensates. Given the low relief and disorganized drainage patterns of this region, dispersal in clastic form in drainage systems is limited and gives rise to erratic distributions. The purpose of this study was to discover whether Au shows significant hydromorphic mobility, which would justify the increasing use that is being made of this element in lake sediments as an indicator for gold mineralization. Waters and lake sediments were collected from Napier Lake, Ontario; PAP Lake, Saskatchewan; and Foster Lake, Manitoba, all of which contain Au-quartz vein mineralization and lie within the glaciated boreal forest zone of the Canadian Shield. In all three areas, profundal lake sediments down-drainage of mineralization contain Au concentrations higher than regional mean concentrations. Significant dissolution and transport of Au was found under oxidizing conditions associated with waters with pH that varied from acid to alkaline. Waters from drill holes penetrating mineralization contain up to 401 ng L-1 Au (note; 1 ng L-1 is equivalent to 1 part per trillion, 10-12). Surface waters overlying or near mineralization collected from bogs, seeps, ponds and streams contain up to 13 ng L-1. The content of Au in lake waters is lower, with a maximum of 1.1 ng L-1. There is also a detectable quantity of Au present in suspensates. Two samples of particulates (> 1 µm) filtered from lake water have Au equivalent to 0.17 ng L-1 and 0.039 ng L-1. While the contents of Au present in solution or as suspensates in lake and stream water are relatively small, they are sufficient, if precipitated, to generate anomalies in lake sediments. Thus for Reservoir Lake, in the Foster Lake area, water from the principal stream entering the lake carries 0.3 ng L-1 Au. This provides an annual flux which far exceeds that required to generate the 7.3 ppb Au contained in profundal sediments of this lake; a content that is anomalous relative to the regional median content of < 1 ppb Au for lake sediments. Hydrogeochemical prospecting involving analysis for Au is one method for tracing the source of anomalous Au in lake sediments. Collection of 1 L samples without field treatment, followed by extraction of Au into MIBK, then analysis by graphite-furnace atomic absorption spectrophotometry, permits detection levels for Au of 0.5 ng L-1. This is below the contents of Au found in some waters from mineralized areas. A detection limit of 0.3 ng L-1 was obtained using larger water samples.