Previously unrecognized glacial erosional landforms (i.e. cirques, u-shaped troughs, truncated spurs and arêtes, in order of increasing doubt), and glacial depositional landforms (i.e. end moraine and possibly ground moraine) occur in the Fifty Mile Creek area, west of the pre-Reid Cordilleran glacial limit. The cirques and end moraine, representing the best evidence of glaciation, are similar to landforms in the adjacent Yukon-Tanana uplands of Alaska and formed during the Eagle glaciation (>40 ka, or Reid in age). Glaciation caused climate-controlled variations in runoff and cycles of aggradation and incision in the Fifty Mile Creek drainage. This resulted in the formation of upper- and lower-level terraces along Fifty Mile Creek and its tributaries. The terraces are composed of slightly muddy, sandy gravel of locally derived lithologies, and are fluvial in origin. Placer gold occurs along Fifty Mile Creek and several of its tributaries, as well as in the lower-level terraces. The upper-level terraces are potentially placer-gold bearing.

A regional till geochemistry project was completed in conjunction with bedrock mapping across rocks of Yukon-Tanana Terrane and North American affinity in central Yukon. The high mineral potential of the area is based on recent discoveries in the Finlayson Lake area to the southeast, an area thought to juxtapose the Glenlyon area prior to displacement on the Tintina Fault. The study area lies at the limit of the Late Wisconsinan McConnell glaciation. Ice flow was largely directed by topography. Soil profiles reveal a veneer of White River ash and loess over most till deposits. Geochemical results from 285 till samples highlight new anomalies in gold, gold/arsenic (intrusive- and fault-related), copper (veins), copper/nickel (ultramafic rocks) and zinc (sedimentary-exhalative (SEDEX) and epithermal). An orientation survey was completed at the Clear Lake SEDEX deposit to evaluate the extent of glacial dispersion down-ice from mineralization.

Much of the Yukon-Tanma Terrane escaped Pleistocene glaciation with the result that there is <1% outcrop across much of the terrane and weathered rock commonely extends to depths of >75m. Weathering has in many cases removed all obvious signs of mineralization and has resulted in the dispersion of soluble metals in the near surface. For these reasons, exploration based on traditional prospecting methods and soil geochemical surveys has met with limited success. Geological mapping is hindered by the lack of exposure and by the complex geology. To address these problems a detailed airborne geological sruvery, combining gamma ray spectrometric, magnetic and VLF sesors, was flown in the Dawson Range, central Yukon Tanana Terrane. Spectrometric data were used to determine the average surface concentration of potassium (K), uranium (U), and thorium (Th). Lithological units are characterized by relatively consistent geochemical signatures permitting improved geological mapping based on the distribution of spectrometric domains. Alteration halves, commonly characterized by the addition of K and magnetite, are identifiable as areas of low Th'K rations and as total field magnetic highs.

A copy of this thesis is available at the EMR library – QE579 P66. This thesis is available online at https://curve.carleton.ca/f7ba3e6b-1aee-4bca-9649-b9c989517ead.

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Two tills and related deposits are the products of at least two ice advances over the Tintina Trench near Ross River, Yukon Territory. These ice advances are termed the McConnell and pre-McConnell glaciations. Erosional remnants provide evidence of the pre-McConnell glaciation and indicate that the ice was flowing to the west or northwest. The onset of McConnell glaciation was marked by an early ice advance out of the Lapie River valley, which was followed by a general ice flow toward the west or northwest along the Tintina Trench. During the retreat of the McConnell glacier, an ice tongue advanced up the Lapie River valley, blocking the drainage and forming a glacial lake. To develop and apply drift prospecting techniques in the Tintina Trench, 204 till samples were collected over the study area. The silt plus clay size fraction was analysed for Au and the clay fraction was analysed for 30 elements. Only Au, Ag, Hg and Sb results are discussed in this paper. The geochemical data for till down-ice from the Grew Creek Au-Ag mineralization (MINFILE 105K 009) show a dispersal train for gold, but not for pathfinder elements such as Ag, As, Hg and Sb. A possible relationship between Au and Tertiary volcanic rocks is illustrated. However, closer-spaced samples would have to be taken to verify this hypothesis, since the length of the Au dispersal train is about 500 m, much smaller than the sampling interval.

Weasel Lake map area (105G/13) is located at the northwestern end of the Finlayson Lake belt (displaced Yukon-Tanana Terrane) and extends northward into ancient North American rocks. Several volcanogenic massive sulphide deposits including: Wolverine, Kudz Ze Kayah, Fyre Lake and the Ice, have been discovered in this part of Yukon-Tanana Terrane, which makes this region one of the most prospective areas of Yukon. Limited outcrop exposure, due to widespread Quaternary cover, has made prospecting challenging in many parts of this terrane, including Weasel Lake map area. Surficial geological mapping and till geochemical sampling was conducted in the map area to better understand its mineral potential. Ice-flow over the area trended at approximately 305° and remained topographically unobstructed through the last glacial maximum. As a result, basal till was deposited across most of the map area. Late glacial deposition of glaciofluvial sediment and meltout till was more common in the northeast part of the map and along the Pelly River. Results of the till geochemical sampling program highlighted anomalies in base-metal elements, platinum/palladium indicators, as well as a gold indicator suite, suggestive of epithermal mineralization.

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Between the Cretaceous granitic rocks (Hake Batholith on the west; Cassiar Batholith to the east) are three belts of metamorphic rocks, collectively part of Yukon-Tanana terrane. These are remnants of oceanic and continental volcanic arcs, and marginal basin sediments of Early to mid-Paleozoic age. At the head of Borden Creek are thick carbonate and andesitic volcanic rocks correlated with Klinkit Group. The Ram Creek fault and Hidden Lake fault are not exposed but deduced to be steeply dipping brittle structures with northeastward thrust or transpressional offset, based upon more complete exposure to the southeast in 105B/3 map area. The former is likely of Cretaceous age; the latter was active between mid-Permian and Early Jurassic time.

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.