The TREK Project is a multi-year activity focused on generating a new geological understanding of part of the Interior Plateau of British Columbia. The project involves several integrated geochemical, geophysical and geological studies over this area, where rocks of the Stikine Terrace are mantled by younger volcanic rocks and glacial deposits. Although vast regions within the TREK study area have been covered by previous geochemical surveys of lake, stream sediment, water, till and biological materials (Jackaman et al., 2015; Sacco and Jackaman, 2015),several key tracts of prospective ground still have limited or no geochemical coverage. The thick vegetation cover, few lakes and limited road networks in these areas has limited the types of survey techniques that could be applied. To address this problem, this study conducted a helicopter-supported, spruce-top twig-and-needle survey to test the feasibility of this type of approach and to generate new geochemical information that can be us ed to help locate hidden mineralization.
This 1000 km2 biogeochemical survey area is located 40 km north of Anahim Lake within the Fraser Plateau and extends north from the Itcha and Ilgachuz mountain ranges to the West Road (Blackwater) River Basin. The area is characterized by gentle north-facing slopes that are blanketed with glacial drift and dissected by streams that flow into the flat-floored valley.
The survey was conducted durings ix-day period in June 2015. A total of 421 side-branch samples, comprising twigs,needles and cones, were systematically collected near the tops of 399 healthy spruce trees spaced 1500 metres apart. For each 1 kg field sample, cones were removed and the branches were trimmed to include only 5--7 years of growth. Approximately 500 g samples were sent to a commercial analytical laboratory for drying and separation into twigs and needles. The twigs were macerated to 1 mm size and a 1 g split digested in HNO3 then aqua-regia and analyzed for 53 elements by inductively coupled plasma--mass spectrometry (ICP-MS). A 50 g split of dry needles were reduced to ash at 475°C and approximately 0.25 g of ash material was analyzed for 53 elements plus rare-earth elements by ICP-MS following aqua-regia digestion.
This report is a data release that includes a Summary Report outlining the survey details, sample collection methods and analytical methods. Field observations and analytical results are presented in Appendix A and summary statistics of individual elements are presented in Appendix B. Appendix C contains a suite of maps in pdf format, including a sample location map, bedrock and surficial geology map, airborne geophysical maps, as well as proportional symbol and gridded image maps for a selection of metals in twigs and ashed needles. The raw datasets are included in excel format, together with a README file with additional details. A complete list of elements and analytical detection limits for both macerated twigs and ashed needles is provided in Tables 1 and 2