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Yukon Geological Survey

YGS Publication Details


Reference Number
1987-2(G)
Title
Geology of Mt. Nansen (115I/3) and Stoddart Creek (115I/6), Dawson Range, Central Yukon
Reference Type
Indian & Northern Affairs Canada/Department of Indian & Northern Development: Exploration & Geological Services Division
Document Type
Open File (Geological - Bedrock)


General Information

Abstract: 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.
Authors: Carlson, G.G.
Map Scale: 1 : 50000
NTS Mapsheet(s): 115I03, 115I06
Citation: Carlson, G.G., 1987. Geology of Mt. Nansen (115I/3) and Stoddart Creek (115I/6), Dawson Range, Central Yukon. Yukon Geological Survey, Open File 1987-2(G).

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Location Map

NTS Mapsheet(s): 115I03, 115I06

Related Occurrences

Name Number Type Status
Rico 115I 080 Hard-rock Anomaly
Granger 115I 050 Hard-rock Drilled Prospect
Rusk 115I 096 Hard-rock Showing
Dows 115I 119 Hard-rock Prospect
Emmons Hill 115I 055 Hard-rock Drilled Prospect
Castle 115I 051 Hard-rock Showing
Tinta Hill 115I 058 Hard-rock Deposit
Cyprus 115I 066 Hard-rock Drilled Prospect
Caribou Creek 115I 049 Hard-rock Past Producer
Webber 115I 065 Hard-rock Deposit
Antoniuk 115I 111 Hard-rock Deposit
Central Klaza 115I 067 Hard-rock Deposit
Eastern Dickson 115I 117 Hard-rock Drilled Prospect
Val 115I 016 Hard-rock Showing
Huestis 115I 138 Hard-rock Past Producer
Laforma 115I 054 Hard-rock Deposit
Bath 115I 088 Hard-rock Anomaly
Grizzly 115I 122 Hard-rock Drilled Prospect
Dade 115I 148 Hard-rock Showing
Ang 115I 123 Hard-rock Showing

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