The northern half of the Jennings River (104O) and southern half of the Wolf Lake (105B) map areas include polydeformed and metamorphosed rocks of the eastern Big Salmon Complex (Yukon-Tanana Terrane) and a succession of mostly Paleozoic rock assemblages currently grouped in Dorsey Terrane. On the northeast side of Dorsey Terrane, siliceous grits and mafic metavolcanic rocks of the Dorsey assemblage are thrust over the Ram Creek assemblage. Dorsey assemblage is in turn structurally overlain by thin mafic volcanic rocks and limestone (Klinkit (?) assemblage), and by dark phyllitic rocks and quartzites of the Swift River assemblage. Extensive stratabound pyrrhotite-sphalerite mineralization occurs along a 6.5 km structural trend in calc-silicate rocks and rhyolite of the Ram Creek assemblage. Similar mineralization also occurs several kilometres southwest of that trend, within or adjacent to the Dorsey assemblage. Both assemblages contain quartz +/- feldspar -phyric layers with potential for volcanogenic massive sulphide showings.

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).

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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A copy of this thesis is available at the EMR library – QE195 C56, This thesis is available online at https://archive.org/details/Cholach1969/mode/2up.

Pentlandite-bearing serpentinized ultramafic flows with a komatiitic composition have been identified within volcano-sedimentary stratigraphy in the Nadaleen Range. Associated listwaenites or silica-carbonate-fuchsite-altered serpentinites carry locally significant gold, copper, nickel and cobalt values. The occurrence of laterally extensive ultramafi c units at the northern edge of the Selwyn Basin remains difficult to explain within the current scope of geological knowledge in the area. However, it represents a new style of exploration target for copper-nickel-bearing massive sulphide deposits, as well as listwaenite-associated gold.

A copy of this thesis is available at the EMR library – TN785 L42 1973. This thesis is available online at http://hdl.handle.net/2429/32084.

Geological map including geological cross sections, mineral occurrences and preliminary isotopic age determinations.

Geological map including isotopic age determination, fossil occurrences and mineral occurrences.