Regional till surveys covering parts of 1:50000 scale NTS map sheets 092L/05 (Mahatta Lake), 092L/06 (Alice Lake), 092L/11 (Port McNeill) and 092L/12 (Quatsino) were completed in the 1990s by the British Columbia Geological Survey Branch (BCGS) as part of the northern Vancouver Island Drift Prospecting Program (Bobrowsky and Sibbick, 1996). The original data publication included inductively coupled plasma atomic emission spectroscopy (ICP-AES), instrumental neutron activation analysis (INAA) and whole rock analytical results for approximately 430 basal till and colluviated till samples.
Recognized as a cost-effective means of updating information collected during older government funded regional geochemical surveys, sample reanalysis by inductively coupled plasma-mass spectrometry (ICP-MS) has significantly improved the BC geochemical database by providing a wide range of new analytical information at improved detection levels plus greater data compatibility with analytical methods currently being employed (Jackaman and Lett, 2013).
Geoscience BC Report 2013-12 presents new ICP-MS results for 433 till samples collected during the original northern Vancouver Island till surveys done in the 1990s. These new results provide a coherent dataset when combined with the results from the new sampling completed in 2012 (see Geoscience BC Report 2013-11). The silt and clay fractions for these till samples, plus 36 quality-control samples, were delivered to Acme Analytical Laboratories Ltd. (Vancouver, BC) and analyzed by an ultra-trace aqua-regia digestion (0.5 g) ICP-MS technique for 53 elements. ICP-MS results have been provided in the Microsoft® Excel (XLS) file GBC REPORT 2013-12.XLS. The data have been carefully checked for analytical quality using blind duplicate samples and control reference material. When determined to be complete and accurate, the reanalysis data were merged with sample site location information downloaded from the BCGS website.