This paper serves as an update to an earlier paper published by the Yukon Geological Survey: New mineral potential mapping methodology for Yukon: case studies from the Beaver River and Dawson regional land use planning areas (Bullen, 2020). Since the release of the earlier paper, a number of the methods have been modified, and new techniques introduced. These are incorporated into this update paper — the reader is referred to the earlier paper for details of the method itself. Mineral potential maps have thus far been completed for the Beaver River watershed, and the Dawson, Teslin, Na-Cho Nyäk Dun, and Ross River regions. There have been significant updates made to the mineral potential mapping method: 1. Modifications to buffer distance and factors (these are an important fuzzy logic (i.e., non-Boolean) component of the mineral potential mapping process) to enhance mapping outcomes. 2. The introduction of an in-house generated, machine learning algorithm (unsupervised, clustering-type) to classify mineral potential in order to remove the potential for human bias. The method replaces the statistical, areas-under-the-curve approach used previously. 3. A new method for delineating anomalous stream sediment data based on the lithological makeup of each watershed basin. The method computes and compares expected assay values to actual assay values, with values exceeding a certain threshold taken as anomalous. The previous method did not take lithology into account, relying on simple percentile methods only, and was considered insufficiently robust. 4. A new method for categorizing mineral potential confidence. Mineral potential maps produced by the Geological Survey contain measures of bedrock mapping confidence to facilitate land use planning. The updated method is significantly more robust than that used previously. 5. Revisions to the map legend to account for the new, machine learning-based mineral potential categorization methodology. 6. Revisions to the map colour scheme to make them colour blind-safe.

Territory-wide mineral potential mapping in Yukon was last conducted 18 years ago. An updated suite of maps for land use planning is, therefore, necessary. The YGS has developed a new GIS-based mapping process for this purpose. Industry-based applications using the new method will be developed going forward. The approach makes use of mineral system components that potentially contribute to metal accumulations in an area. The method is a hybrid between a classic data-driven probabilistic approach and an expert-driven fuzzy logic approach. It is non-specific in terms of commodity and/or deposit type – however, the claim and assessment report footprint data that are integral to the mapping process capture these important components. The procedure makes use of block modeling techniques where each block is assigned a prospectivity and (bedrock mapping) confidence score. Calculations are based on the presence or absence of categorical features within unit cells, and the scores represent the posterior favourability of each cell. Evidential layers are weighted according to buffer distance and/or through the application of knowledge-based factors. Lithology classes are factored using a multiclass weights-of-evidence approach. Mineral potential and confidence scores are converted to either a 1, 2 or 3 according to a defined mathematical schema. The values are then combined – blocks with scores of 1:1 have the lowest mineral potential/lowest confidence whereas blocks with scores of 3:3 have the highest mineral potential/highest confidence. Nine possible combinations exist. Mineral potential maps containing measures of both potential and confidence are generated based on the cumulative contrast values. Areas cut by major structures along which significant displacement has occurred need to be evaluated separately, and then stitched back together at the end of the assessment process. Concurrently, the mineral potential data need to be leveled to account for prospectivity differences across the structure concerned.

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