Geological map of Quartet Lakes map area (NTS 106E/1), including a geological cross section and mineral occurrences.

The study area is underlain by four stratigraphic successions ranging in age from Middle Proterozoic to Early Paleozoic. From oldest to youngest, they are: Middle Proterozoic Wernecke Supergroup; Middle to Upper Proterozoic Pinguicula Group; Upper Proterozoic Windermere Supergroup; and Uppermost Proterozoic to Lower Paleozoic sandstone and carbonate. Together, they represent about a billion years of intermittent sedimentation punctuated by processes such as deformation, uplift, erosion, magmatism and mineralization. Rocks in the study area record eight phases of contractional and extensional deformation, some of which may be related to strike-slip faulting. Two phases of southwest-verging folds and thrust faults may be related to dextral transpression on the Snake River Fault. Mineral enrichments occur in two general forms:: breccia-related (Middle Proterozoic), and veins (Mesozoic to Tertiary). The breccia-related occurrences have enrichments of Cu ± U, Co, Au and Ag, as dissemminations and veinlets in and near intrusive breccia zones (Wernecke breccia). The vein occurrences comprise Zn-Pb-Ag ± Cu and Au, in veins and related lenses and irregular replacements of carbonate.

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The Fairchild Lake map area is underlain by two principal sedimentary successions, Middle Proterozoic Wernecke Supergroup and unconformably overlying Middle to Late Proterozoic Pinguicula Group. The angular unconformity between the successions was caused by an intervening period of deformation known as Racklan orogeny. A third succession, herein named the Slab volcanics, is inferred to have been deposited after Racklan orogeny and before Pinguicula Group deposition. Mineralization occurs as sedimentary exhalative, vein, and intrusive breccia occurrences within Wernecke Supergroup. The sedimentary exhalatives contain Zn, Pb, Cu and Ag in shaley horizons within a mainly dolomitic sequence. The vein occurrences contain Zn, Pb, Cu, Ag, Au and U. The intrusive breccias, collectively known as Wernecke breccia, host Cu, Co, U, Ag and Au. Wernecke breccia was probably generated by explosive expansion of volatile-rich fluids. Brecciation was preceded by Racklan orogeny and intrusion of igenous dykes. The dykes and the breccia-related mineralizing fluids may have a common source in postulated underlying magma chambers. Local supergene enrichment of breccia mineralization was caused by Middle to Late Proterozoic weathering before deposition of Pinguicula Group.

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Yukon-Tanana Terrane in Grass Lakes map area south of Finlayson Lake consists of highly deformed though regionally mappable metasedimentary and metavolcanic rocks. Four newly revised map units and various subunits have been traced throughout the area. These include unit 1, a quartz-rich metaclastic unit with felsic metavolcanic rocks at its lowest exposed level and a middle calcareous marker; unit 2, a mafic metavolcanic unit with lesser carbonaceous metasedimentary rocks; unit 3, a carbonaceous phyllite and quartzite and felsic metavolcanic unit, and unit 4, an upper unit of carbonaceous phyllite, mafic metavolcanic rocks and coarse-grained quartzofeldspathic metaclastic rocks. Units 2 and 4 have been redefined from a previous report based on new observations and a consideration of the provenance of coarse-grained quartzofeldspathic metaconglomerates now included in unit 4. In the current interpretation, the metaconglomerate-bearing strata north of and overlying the felsic meta-volcanic rocks hosting Kudz Ze Kayah are considered to unconformably overlie them. Three of these map units are associated with mineral occurrences or deposits. Rusty, locally malachite-stained muscovite-quartz schist at Arcturus Resources' First Base claims and Expatriate Resources' Blue Line and Winger claims belong to the felsic metavolcanic part of unit 1. Columbia Gold's Fyre Lake deposit is hosted in unit 2 mafic metavolcanic rocks, possibly associated with a synvolcanic fault. Cominco's Kudz Ze Kayah deposit occurs in unit 3 felsic metavolcanic rocks. Gossans on Cominco's Cobb claims, Expatriate's Overtime and NHL claims, and Atna/Westmin's Pack claims and anomalous copper in soils at Arcturus' Bas claims are also spatially associated with this unit.

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Thirty-Seven Mile Creek map area, northwest of Whitehorse, straddles the contact between Coast Plutonic Complex and rocks attributed to northern Stikine Terrane. Late Triassic Little River granodiorite and Late Paleocene (57 Ma) Annie Ned granite underlie the western part of the map area. Upper Triassic to Middle Jurassic volcanic and sedimentary rocks of the Lewes River and Laberge groups underlie the eastern part of the map. The contact between Coast Plutonic Complex and Stikine Terrane is marked by the Takhini deformation zone - a region of greenschist, gneiss, mylonite, and amphibolite whose protolith is volcanic rocks of Lewes River Group. Potential mineral deposits in this map area include epithermal and mesothermal quartz veins, and magnetite skarns.

Paleozoic rocks of the Pelly Mountains, central Yukon, preserve greater than 150 m.y. of sedimentation, magmatism and base-metal mineralization. To identify secular trends in regional tectonics and metallogeny, a multi-year project on the stratigraphy of the Pelly Mountains in the Quiet Lake (105F) and Finlayson Lake (105G) map areas was initiated. Field studies during summer 2015 focused on two stratigraphic intervals: (1) mafic volcanic, volcaniclastic and clastic rock successions assigned to the Cambrian-Ordovician Cloutier and Groundhog formations (Kechika group); and (2) felsic volcanic, volcaniclastic and clastic rock successions assigned to the Devonian-Mississippian Black Slate and Felsic Volcanic formations (Seagull group). Cambrian-Ordovician strata were deposited in a marine environment characterized by episodic mafic volcanism and extensional tectonism. Devonian-Mississippian strata record the transition from an extensional turbidite basin to a metalliferous volcanic rift basin, and resemble key rock assemblages of the Selwyn basin (Earn Group) and Yukon-Tanana terrane (Grass Lakes and Wolverine Lake groups).