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TitleA review of analytical methods for regional geochemical survey (RGS) programs in the Canadian Cordillera
AuthorLett, R; Rukhlov, A S
SourceIndicator minerals in till and stream sediments of the Canadian Cordillera; by Ferbey, T (ed.); Plouffe, AORCID logo (ed.); Hickin, A S (ed.); Geological Association of Canada, Special Paper vol. 50, 2017 p. 53-108
Alt SeriesMineralogical Association of Canada, Topics in Mineral Sciences 47
PublisherGeological Association of Canada
PublisherMineralogical Association of Canada
RelatedThis publication is contained in Indicator minerals in till and stream sediments of the Canadian Cordillera
ProvinceBritish Columbia; Yukon
NTS82; 83; 84; 85; 92; 93; 94; 95; 96; 102; 103; 104; 105; 106; 107; 114; 115; 116; 117
Lat/Long WENS-141.0000 -113.5000 70.0000 48.0000
Subjectseconomic geology; surficial geology/geomorphology; geochemistry; mineral deposits; mineral exploration; prospecting techniques; drift prospecting; geochemical surveys; sediments; glacial deposits; tills; fluvial deposits; lacustrine deposits; surface waters; lake water geochemistry; stream water geochemistry; groundwater; organic deposits; heavy mineral samples; vegetation; sampling methods; analytical methods; sample preparation; colorimetric analyses; trace element analyses; neutron activation analyses; spectroscopic analyses; mass spectrometer analysis; isotopic studies; major element analyses; minor element geochemistry; grain size analyses; size fractionation; pebble lithology; heavy mineral analyses; scanning electron microscopy; provenance; history; Canadian Cordillera; Quality control; Phanerozoic; Cenozoic; Quaternary
Illustrationslocation maps; tables; flow diagrams; bar graphs
ProgramTargeted Geoscience Initiative (TGI-5) Porphyry systems
Released2017 01 01
AbstractCommonly sampled media for regional geochemical survey (RGS) programs in Canada are stream and lake sediments and waters, and till deposits. During the last 60 years in the Canadian Cordillera of British Columbia and Yukon, surveys have advanced by sampling more diverse media such as moss mat sediment, stream heavy mineral concentrates, vegetation, and using increasingly sophisticated analytical methods. In the 1950s, stream-sediment samples collected by mining companies as part of regional geochemical surveys were typically analyzed for a small number of elements by colorimetric techniques. Later Canadian government-managed regional geochemical surveys used other sample types (e.g., lake sediment and water), initially to locate strategic metals (e.g., uranium) and later to detect other metals. For these surveys sample densities range from one sample per 5-10 km2 for till and vegetation to one sample per 10-15 km2 for stream and lacustrine sediments. Samples from these surveys were analyzed for a greater number of elements by a combination of colorimetric, fluorimetric and acid digestion-atomic absorption techniques. A greater appreciation of Cordilleran glacial geology and ice-flow patterns led to till geochemistry being successfully used to detect new sources of bedrock mineralization concealed beneath locally transported surficial cover. At the same time as new sample media were being applied to regional geochemical surveys, new analytical methods were being developed, such as instrumental neutron activation (INAA), aqua regia digestion followed by multi-element analysis by inductively coupled plasma emission spectroscopy (ICP-ES) and, later, mass spectroscopy (ICP-MS). Over time, the development of systematic quality control schemes for sampling and sample analysis and new standard reference materials by the Geological Survey of Canada improved the reliability of regional survey geochemical data. Routinely sampled as part of regional geochemical survey (RGS) programs in the Canadian Cordillera are stream and lacustrine sediments and waters, vegetation, and till deposits.
Since 2000, heavy mineral (e.g., >SG 3.2) concentrates recovered from the <2 mm grain-size fraction have been prepared from many stream-sediment and till samples collected in British Columbia. After microscopic examination, these concentrates are analyzed by methods such as scanning electron microscopy (SEM) combined with Energy Dispersive X-ray Spectroscopy (EDS) to identify and count gold, platinum, sulphide, oxide, and silicate grains. Different deposit types contributing to the mineral suite in a sample can be distinguished from different indicator mineral assemblages such as diamond indicator minerals, magmatic/metamorphosed massive sulphide indicator minerals or porphyry Cu indicator minerals. Other micro-analytical methods such as in situ high-precision isotope analysis and laser ablation followed by ICP-MS can also be applied to better identify mineralized source rocks of heavy mineral concentrates. Combining heavy mineral studies with the results of sediment and till sample geochemistry has added a new dimension to applying regional survey data to explore for new mineral resources in the Cordillera.

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