Yukon Geological Survey publication metadata (English, HTML)

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2026-08-26

The geology in the Mount Nansen area, of the Dawson Range, comprises a metamorphic basement overlain and intruded by mid and Late Cretaceous magmatic rocks. Mid-Cretaceous epithermal deposits are recognized in the Brown-McDade cluster in the south, and Late Cretaceous porphyry and epithermal occurrences in the centrally located Klaza cluster. Here we report eight new U-Pb zircon crystallization ages, two CA-TIMS and six LA-ICPMS, and Pb isotopic data for igneous feldspar from six samples. A 199.06 ± 0.96 Ma crystallization age demonstrates the host rock to the Brown-McDade deposit is the Late Triassic to Early Jurassic Minto suite. We report crystallization ages of 111 ± 1.8 Ma for the Dickson Hill porphyry, 107.96 ± 0.03 and 107.86 ± 0.03 Ma for the central and border phases of the Bow Creek granite, respectively, and 107.0 ± 0.72, 107.0 ± 0.78 and 107.5 ± 0.67 Ma for equigranular and porphyritic phases of the Dawson Range granodiorite. These ages confirm a mid-Cretaceous Whitehorse suite affinity for these rocks with porphyritic textures suggesting high-level emplacement. Feldspar Pb isotopic data of igneous rocks in the Mount Nansen area become more radiogenic with time and…

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