Abstract: The Mount M'Clintock map area, northeast of Whitehorse, is dominated by Middle Triassic to Jurassic sedimentary and volcanic strata of Stikinia with small portions of the Cache Creek and Yukon-Tanana Terranes. These assemblages were deformed prior to the mid-Cretaceous intrusion of three plutonic suites and the deposition of two suites of volcanic rocks.

Sedimentary rocks previously mapped as undifferentiated Lewes River and Laberge Group strata are separated into their respectve groups and further sub-divided into several members. Lewes River Group rocks form three units that are Carnian and older, Norian, and Upper Norian in age and are represented by siliceous siltstone and calcareous sandstone, conglomerate and limestone respectively. Laberge Group strata are divided according to lithology and dominated by siltstone-sandstone couplets and massive siltstone with lesser conglomerate and volcanogenic sandstone. Volcanic rocks previously mapped as Hutshi Group are divided into the dominantly mafic and submarine, MiddleTriassic Joe Mountain volcanic complex (JMVC) and the dominantly felsic and sub-aerial Mount Byng volcanic complex (BCVC). The volcanic and sedimentary rocks generally increase in age from Middle Triassic to Jurassic from west to east across the map area.

Plutons cutting these strata belong to the M'Clintock Lakes (120 Ma), the Whitehorse (115 Ma), and the Mount McIntyre (109 Ma) plutonic suites. The predominantly felsic fragmental rocks of the BCVC are genetically associated with the Byng Creek pluton of the Mount McIntyre plutonic suite. The BCVC is nested into the country rocks and its eastern margin and is preserved as the rim of a tilted caldera.

Strata of the Laberge and Lewes River groups are folded throughout. Wavelengths are on the order of approximately 1-2 km, but are much tigter in black siltstone units and adjacent to northwest-trending faults. Faults are ubiquitous throughout the map area and form three sets. North-trending faults are the most common. They are spaced a few kilometres from each other and dictate the physiography and drainage of the region. Northwest-trending faults, in the northeastern corner of the map area control the Teslin River valley and juxtapose Yukon-Tanana rocks with Stikinia. Older faults are dominantly east-trending but are terminated or reactivated by younger faults.

Copper (gold-molybdenum-tungsten) skarns and gold-bearing quartz veins are the two mineral deposit types most likely to be discovered in the map area. The source of the placer gold in Sheldon Creek is unknown but may be related to gold veins in the JMVC, BCVC, Sheldon Creek volcanics or the surrounding sedimentary rocks. Hydrothermal activity in the JMVC is characterized by orange weathering alteration, breccias, and carbonate veins. Cache Creek rocks in the southern part of the map area are targets for listwaenite associated gold veins.

Authors: Hart, C.J.R. and Hunt, J.A.

Map Scale: 1 : 0

NTS Mapsheet(s): 105D16

Citation: Hart, C.J.R. and Hunt, J.A., 1995. Geology of the Mount M'Clintock Map Area (105D/16), Southern Yukon Territory. In: Yukon Exploration and Geology 1994, Yukon Geological Exploration , Indian & Northern Affairs Canada/Department of Indian & Northern Development: Exploration & Geological Services Division, 87-104.

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