The Mount Skukum Volcanic Complex (MSVC) is the northernmost extension of the Sloko volcanic province in western British Columbia, a broad northwest-trending volcanic belt along the northeast margin of the Coast Plutonic Belt. Rocks of the Sloko volcanic province are preserved as downfaulted blocks and as erosional remnants on higher upland surfaces. They comprise an assemblage of intermediate to felsic volcanic rocks and derived sedimentary rocks that lie unconformably on Cretaceous granitic rocks, folded Jurassic rocks and Precambrian (?) metasedimentary rocks. The MSVC is Paleocene-Eocene in age, and elliptical in plan; it covers an area of about 140 km squared. It is a downfaulted volcanic block, deposited on Cretaceous granitic rocks of the Ruby Range Batholith and older metasedimentary rocks of the Yukon Group. The complex is surrounded peripherally by several high-level rhyolite intrusions which have recently been dated at 53 ±1.1 Ma using rubidium-strontium geochronology. The MSVC has a maximum vertical thickness of 850 m. It includes:: 1) a downfaulted part of an andesitic stratovolcano which forms the western and southern parts of the complex and comprises the distal and medial facies assemblage of Formations 1 and 2, and the more proximal facies assemblage of Formation 3 a small felsic cauldron subsidence structure in the northeast corner of the area represented by the felsic cauldron-fill deposits of Formation 4; 3) an andesitic vent facies environment located in a small area in the midwestern part of the complex and comprising the deposits of Formation 5; and 4) a central quartz-feldspar-phyric rhyolite intrusion along the western boundary of the small felsic cauldron. A NNE-trending fracture system is the dominant and perhaps the latest structural feature in the MSVC. Economic epigenetic gold veins are found in three major subparallel NNE-trending fault zones. The veins consist of quartz and calcite and are unusual in that they contain no sulphides and have poorly developed wall rock alteration. As of February 1984, the average grade was 27 g/t gold and 22.63 g/t silver with proven reserves of 149,114 tonnes.

Preliminary geological map (1:50,000 scale) of Mount M'Clintock area, southern Yukon (NTS 105D/16) including geological cross sections and mineral occurrences.

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Geological map (1:50,000 scale) of Mount M'Clintock map area, southern Yukon (NTS 105D/16) including geological cross sections and mineral occurrences.

Geological map (1:50,000 scale) of Mount Haldane area, central Yukon including geological cross sections, structural relationships and mineral occurrences.

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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.

The Eocene Skukum volcanic complex, 60 km south-southwest of Whitehorse, is elliptical in plan, covers an area of about 140 km², and unconformably overlies Cretaceous granitic rocks and Precambrian metasedimentary rocks. The complex is fault-bounded and in places has been intruded by felsic dykes and stocks. A major north-trending fault divides the area into two parts: a western part which includes a lower interlayered sedimentary-volcanic sequence and an upper unit, approximately 500 m thick, characterized by andesite lava flows, pyroclastic flows and sedimentary units; and an eastern part which comprises about 800 m of altered felsic pyroclastic flows and brecciated, flow layered and spherulitic felsic lava flows. Study of the interlayered sedimentary-volcanic formation provides a control on the paleotopography of the Skukum area, and the depositional environment and provenance of the formation..

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