The Geological Survey of Canada (GSC) has developed field and lab methods protocols to guide till sample collection, processing, geochemical analysis of the till matrix, monitoring of quality assurance/quality control, and archiving procedures for reconnaissance- to local-scale geochemical surveys. The most significant concepts and procedures are described in this paper. Continued and long-term use of these protocols will ultimately allow GSC researchers to integrate and contrast multiple datasets and ensure minimum levels of quality assurance and control for all till geochemical data. This set of protocols is the first established for Canadian till sampling and analysis and represents a contribution to the GSC’s Geo-mapping for Energy and Minerals (GEM) Program. Sharing the GSC’s knowledge on till sampling and analysis with the international community will allow other researchers and explorationists to adopt similar procedures. This sharing of knowledge will ultimately allow comparison of till geochemical datasets from various parts of Canada and internationally as well as ensuring a minimum level of quality assurance and control for all till geochemical data.
A successful method of mineral exploration in glaciated terrain is the use of indicator minerals recovered from carefully selected glacial sediments, and subsequently traced back to their bedrock source. The successful application of indicator mineral methods relies on efficient and effective recovery as well as the correct identification of a wide variety of indicator minerals. The Geological Survey of Canada (GSC) has developed protocols for ongoing and future research projects to achieve the highest quality for reporting indicator mineral data. Such protocols include the use of field duplicate samples, blank samples, and base material spiked with known numbers, morphologies, species, and sizes of indicator minerals. Field duplicate samples serve to estimate sediment heterogeneity. Spiked samples are used to monitor the accuracy of the sample processing and mineral identification methods for recovering specific minerals. Blank samples serve to detect potential carry-over contamination. In certain instances, a specific sample processing order is essential and should be communicated to the commercial processing laboratory. Ore-rich samples collected near known mineralization are to be processed last, to reduce chances of carry-over contamination. Repeated indicator mineral counts should be carried out on at least 10% of the heavy mineral concentrates to measure reproducibility (precision) of the mineral counts. All indicator mineral data, original laboratory reports, heavy mineral concentrates, unmounted picked grains, and grain mounts are now archived at the GSC, using specific guidelines.
The Geological Survey of Canada carried out reconnaissance-scale to deposit-scale geochemical and indicator-mineral surveys and case studies across northern Canada between 2008 and 2020 as part of its Geo-mapping for Energy and Minerals (GEM) program. In these studies, surficial geochemistry was used to determine the concentrations of up to 65 elements in various sample media including lake sediment, lake water, stream sediment, stream water, or till samples across approximately 1 000 000 km2 of northern Canada. As part of these surficial geochemistry surveys, indicator mineral methods were also used in regional-scale and deposit-scale stream sediment and till surveys. Through this program, areas with anomalous concentrations of elements and/or indicator minerals that are indicative of bedrock mineralization were identified, new mineral exploration models and protocols were developed, a new generation of geoscientists was trained, and geoscience knowledge was transferred to northern communities. Regional- and deposit-scale studies demonstrated how transport data (till geochemistry, indicator mineral abundance) and ice-flow indicator data can be used together to identify and understand complex ice flow and glacial transport. Detailed studies at the Izok Lake Zn-Cu-Pb-Ag VMS, Nunavut, the Pine Point carbonate-hosted Pb-Zn in the Northwest Territories, the Strange Lake REE deposit in Quebec and Labrador as well as U-Cu-Fe-F and Cu-Ag-Au-Au IOCG deposits in the Great Bear magmatic zone, Northwest Territories demonstrate new suites of indicator minerals that can now be used in future reconnaissance- and regional-scale stream sediment and till surveys across Canada.
Geochemical data are complex, and becoming more so as analytical techniques advance. This complexity gives rise to many data management issues that have no simple solutions. The Geological Survey of Canada (GSC) has a long history of collecting and managing geochemical data. The challenges of managing the data are continuously evolving. The emergence of the WWW is causing a revolution in how scientific data are delivered. This paper documents how one group within the GSC is responding to this rapidly changing environment.
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