The accuracy and 95.5% confidence-level precision of the whole-rock geochemical data were estimated in terms of the average percentage recovery (APR) and relative standard deviation (2RSD) values, respectively. However, the 2RSD values include propagated errors of the expected concentrations in the reference materials. Therefore, the 2RSD values also represent uncertainties in the accuracy estimates.
Two certified reference materials (CRMs) were submitted to the lab at regular intervals of approximately 1 CRM for every 20 samples. The two CRMs selected for this project were OREAS 30a (olivine tholeiitic basalt), and OREAS 20a (barren I-Type hornblende-bearing granodiorite).
The average APR of the whole-rock geochemical determinations for OREAS 20a is 99.0%, and 100.1% for OREAS 30a. Accuracy results for individual elements are listed in the "Whole-Rock_Geochemistry_Detection_Limits" file.
The average 2RSD of the whole-rock geochemical determinations for OREAS 20a is 10.4%, and 12.1% for OREAS 30a. Precision results for individual elements are listed in the “Whole-Rock_Geochemistry_Detection_Limits” file.
Where elements are reported from the laboratory but certified values are not reported for the CRM, both APR and 2RSD values are listed as -9999.
Latitude and Longitude are listed as -9999 for all CRM records.
This work used samples from the Precambrian Shield of Alberta rock sample collection housed at the Mineral Core Research Facility of the Alberta Geological Survey. A total of 2303 samples were retrieved from this collection for whole-rock major and trace element determinations. For internal data-quality control an additional 120 certified reference material samples (i.e., OREAS 20a, 30a) were included in this project after every 20th Precambrian Shield sample. A total of 2423 samples are reported. Analysis was by inductively coupled plasma optical emission spectrometry (ICP-OES) or mass spectrometry (ICP-MS). The specific Activation Laboratories Ltd. analyses were:
- Code 4Litho-Research: samples are subject to lithium metaborate/lithium tetraborate fusion within disposable graphite crucibles, the resulting molten bead is digested in a solution of 5% nitric acid and mixed until completely dissolved (~30 minutes). ICP-MS/OES is used to quantify various elements in resulting solution (https://actlabs.com/geochemistry/lithogeochemistry-and-whole-rock-analysis/lithogeochemistry/).
- Code 4B1: samples are digested with four acids beginning with hydrofluoric, followed by a mixture of nitric and perchloric acids, heated using precise programmer-controlled heating in several ramping and holding cycles which takes samples to dryness. After dryness is attained, samples are brought back into solution using hydrochloric acid. ICP-OES is used to quantify base metals in resulting solution (https://actlabs.com/geochemistry/lithogeochemistry-and-whole-rock-analysis/lithogeochemistry/).