The Mount Nansen and Stoddart Creek map areas (NTS 115 I/3, 6) are in the southern part of the Dawson Range. They contain a number of porphyry and vein related mineral occurrences which have been undergoing extensive re-evaluation for precious metals potential. Basement rocks are part of the Yukon Crystalline Terrane and include metamorphosed and deformed sedimentary, volcanic and plutonic rocks of uncertain age. These are intruded by two suites of foliated plutonic rocks, the Upper Triassic to Jurassic Klotassin Suite, mainly hornblende-biotite granodiorite, and the Jurassic Big Creek Suite, including K-feldspar porphyritic syenite, quartz syenite and monzonite. Latest metamorphism of basement rocks is likely related to emplacement of these suites. Latest lower Cretaceous was marked by intrusion of the Dawson Range Batholith, consisting of the regionally exposed Casino Granodiorite and the more localized Coffee Creek Granite. The Mount Nansen Volcanics, mainly andesite with a lesser felsic component, are possibly cogenetic with these intrusives. Numerous intermediate to felsic porphyry stocks and dikes may be of Mount Nansen age in part, but they are at least in part younger. The Bow Creek Granite is a newly defined, high level, granophyric pluton with related, peripheral quartz-feldspar porphyry dikes. These rocks appear to cut the Mount Nansen volcanics and may be as young as the Carmacks volcanism. The Caribou Creek Conglomerate is a very localized sedimentary sequence which underlies the Carmacks volcanics. The Carmacks Volcanic Suite, uppermost Cretaceous in age, is relatively flat-lying and has been subdivided into three units. The lowermost consists of felsic pyroclastic rocks and associated glassy domes or plugs. The middle unit, which appears to be quite thin in the map area, consists of andesite flows and pyroclastics with minor basalt. The most extensive is the upper unit, which consists mainly of basalt flows. Mineral deposits are of four main types, including porphyries, veins, skarns and placer. Transitional varieties are associated with brecciation and porphyry dike emplacement. The porphyries are low grade copper-molybdenum deposits with local gold enrichment in the upper parts. Breccias with elevated precious metal values occur within the porphyries and also peripherally associated with quartz-feldspar porphyry dikes. Gold and silver-bearing quartz veins occur in dilational fracture systems which are also peripheral to the porphyries. In the presence of calcareous meta-sediments of Yukon Crystalline Terrane, gold-bearing, iron-rich skarns have formed. Base metal-rich veins are rare and distal from the porphyry centres. Mineralization controls are recognised as follows:: 1. Proximity to major regional structures such as the Big Creek Fault and the Minto Linear which extends north-northeasterly through the map area. 2. Local structures, ranging in trend from northwesterly to northeasterly, are important as hydrothermal channelways and vein sites. 3. Presence of a favourable host, including Mount Nansen volcanics, siliceous meta-sediments and Casino Granodiorite. 4. Proximity to porphyry stocks or quartz-feldspar pophyry dikes.

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A copy of this thesis is available at the EMR library – EMR Library QE195.A66 1998.

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.

Surficial geological map (1:50,000 scale) of Mount Haldane area, central Yukon (NTS 105M/13) including marginal notes on physiography, glacial history, placer gold potential and terrain hazards.

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A copy of this thesis is available at the EMR library – QE195 D52.

Surficial geological map and till geochemistry (copper, lead and zinc) of Mount Mye area.

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