QA/QC for mineral exploration refers to the planned systems and processes involved in ensuring that sampling, sample preparation, assay, and data processing generate credible and unbiased information. Here, QA involves the design of the system, while QC is the process of continuously testing outcomes using such approaches as standards, blanks, duplicates, and external verification.
For exploration programs, QA/QC begins during sampling since the quality of the resultant resource model hinges on the quality of the samples initially collected. The key here is developing effective procedures for sampling whether core, RC chips, trenches, or grab samples; then labelling, transportation, preparation, and assay of those samples to capture geological rather than laboratory or field errors.
The QC aspect typically involves the introduction of certified reference material, blank samples, and duplicate samples among the batch samples to test for accuracy, contamination, and precision. Such checks will help in the identification of issues like sample cross-contamination, contamination during sample preparation, weak laboratory performance, or biased analysis before using the results in evaluation.
QA/QC is crucial to resource estimation since the mineral resource estimate relies heavily on data that underlie the resource model. Resource estimation involves use of assay information, sampling interval, density information, and geology. Biased or inadequate management of any of the above-listed components will make tonnes or grades underestimated or overestimated.
The reason for this becomes all the more evident when one considers that resource modeling is highly vulnerable to even slight discrepancies in grade information. Inaccuracies in contamination, precision, or sampling can seriously skew grade continuity and result in erroneous cut-offs, tonnage measurements, and economic assessments.
Another reason for having an effective QA/QC process relates to meeting standards and regulatory requirements, which expect exploration results to be repeatable, accurate, and verifiable. As such, QA/QC is not simply some technical exercise to go through, but rather a risk management strategy central to geology and resource assessment.
