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Canadian Geochemical Data ›› Where can you find it? ›› What does it look like?

Canadian Geochemical Data ›› Where can you find it? ›› What does it look like?. S.W. Adcock March 3 rd 2010. What is Geochemistry?. Two quotes: “All of the sciences are subdivisions of geochemistry.” “Why can’t geochemists ever agree on anything?”.

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Canadian Geochemical Data ›› Where can you find it? ›› What does it look like?

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  1. Canadian Geochemical Data›› Where can you find it?›› What does it look like? S.W. Adcock March 3rd 2010

  2. What is Geochemistry? • Two quotes: • “All of the sciences are subdivisions of geochemistry.” • “Why can’t geochemists ever agree on anything?”

  3. Geochemical Data within the scope of this talk • Soil and Till • Different size fractions • Bulk chemistry • Inorganic • Trace elements • NO mineralogy

  4. Producers of geochemical data • Major • GSC • Provincial surveys: QC, ON, BC, NB, NL • Minor • Provincial surveys: AB, SK, MB, NS • Links: http://gsc.nrcan.gc.ca/connections_e.php • Hard-to-find / hard-to-use • Other Government departments, academia, mineral exploration companies, EA reports

  5. Catalogues • GSC • Geoscience Data Repository • http://gdr.nrcan.gc.ca/geochem/index_e.php • Quebec • http://www.mrn.gouv.qc.ca/mines/geologie/geologie-donnees.jsp • BC Map Place • http:mapplace.ca

  6. Geoscience Data Repository Demo • Geochemical metadata home page • http://gdr.nrcan.gc.ca/geochem/index_e.php • Metadata for 600 surveys • ~300 soil and/or till surveys • 65 till surveys have enhanced metadata • User manual • GSC Open File 5936

  7. GDR Demo (cont’d) • Sample metadata page • http://gdr.nrcan.gc.ca/geochem/metadata_svy_e.php?key=210037 • Brief summary of the survey • Links to description of original project and any subsequent projects (re-analyses) • Links to publications • Links to downloadable files (raw data, PDFs etc.)

  8. GDR Demo (cont’d) • Access to enhanced metadata • KML file of 65 enhanced surveys • http://apps1.gdr.nrcan.gc.ca/geochem/kml/index/surveys_ext_e.kml • Periodic Table identifying elements for which KML files are available • http://apps1.gdr.nrcan.gc.ca/geochem/pertable/pertable_e.htm

  9. Explanation of enhanced metadata • http://gdr.nrcan.gc.ca/geochem/metadata_svy_e.php?key=210037 • Sample locations • Sample Types • Prep lab • Analytical History • Bundles – downloadable spreadsheets • Analytical methods • Individual analytical quantities • KML files of analytical values

  10. Enhanced metadata • Sample Locations

  11. Sample Types

  12. Soil vs. Till • User beware – exactly what was sampled? • “B horizon till” ???

  13. Prep Lab materials

  14. Grain size classification

  15. Analytical history

  16. Analytical methods • Three trends over time: • Determination limits are lowered (with a few exceptions) • Number of elements analysed is increasing • 1960s : < 10 elements • 2000s : > 50 elements • Increased automation / multi-element techniques • Less risk of human error • Lower costs

  17. Analytical methods (cont’d) • “Total” vs. “Partial” analysis • Total • 1. Technique does not require dissolution • INAA, XRF • 2. Technique involves total dissolution • Requires nasty chemicals • Partial • Technique involves dissolution by a variety of chemical attacks

  18. Accuracy vs. Precision

  19. Analytical measurementsHow to handle measurements below the determination limit • 3 options • Negative DL: < 2  - 2 • Half DL < 2  1 • Text < 2  < 2 • What if the DL is variable?

  20. Periodic Table, showing analysed elements • http://apps1.gdr.nrcan.gc.ca/geochem/pertable/pertable_e.htm

  21. Additional resources • Environmental Geochemistry textbooks • Frederic Siegel • Statistics for environmental geochemistry • Helsel and Hirsch; downloadable from: • http://pubs.usgs.gov/twri/twri4a3/ • Clemens Reimann et al. (2008) • Data compilations • Dragun and Chekiri • Reimann and de Caritat

  22. Additional resources (cont’d) • Geochemical Atlases • Reimann et al. (1998) Environmental Geochemical Atlas of the Central Barents Region • Reimann et al. (2003) Agricultural Soils in Northern Europe: a Geochemical Atlas • Salminen et al. (2005, 2006) Geochemical Atlas of Europe; Parts 1 and 2 • Journals • Elements • http://www.elementsmagazine.org/

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