This map presents a compilation and re-interpretation of the bedrock geology in the Mount Nansen area. The Mount Nansen porphyry district is herein defined as the area of historic placer gold and hard rock gold-silver production centred on the headwaters of the East Fork of Nansen Creek. The majority of MINFILE occurrences in the district are within a 12 x 6 km, northwest elongate area (Hart and Langdon, 1997) shown at 1:20 000 on sheet 2. In the northwestern part of the district, vein and porphyry mineralization was related to Late Cretaceous porphyritic rocks of the Casino and Prospector Mountain suites. Mineralization in the southeastern part of the district appears to have been primarily related to Early Cretaceous porphyritic dikes and plugs.
Our mapping is combined with previously undigitized 1:30 000 (published at 1:50 0000) bedrock mapping. Geochronological data are from this study, Lee (2021) and the Yukon geochronology database (YGS, 2020b). The location of approximately 20 samples in YGS (2020b) were modified based on field checks and location notes in the database; geochronological samples which could not be confidently located are omitted.