Geological map (1:50,000 scale) of Slats Creek area, Wernecke Mountains, central Yukon (NTS 106D/16) including geological cross sections, mineral occurrences and preliminary isotopic age determinations.

Geological map (1:50,000 scale) of Slats Creek area, Wernecke Mountains, central Yukon (NTS 106D/16) including geological cross sections and mineral occurrences.

Historic placer mining areas in Yukon can be grouped into ten areas: Klondike; Sixtymile; Fortymile; Clear Creek; Moosehorn Range; Stewart River; Clear Creek; Mayo; Dawson Range; and Livingstone Creek. Each area has its own geomorphic setting and depositional history which is related to its glacial history. Several Quaternary glacial advances have been described in Yukon, and these are generally divided into three episodes, commonly known as the pre-Reid, Reid and McConnell, in order of oldest to most recent. Placer deposit in the unglaciated Klondike, Sixtymile, Fortymile and Moosehorn drainages occur in valley-bottoms, alluvial fans, in gulch gravels and as high level terraces. Placer deposits in glaciated areas occur in variably reworked and buried valley-bottom, bench and gulch settings, in auriferous glacial till and glaciofluvial gravels, and in non-glacial gravels which were deposited on top of glacial drift. Targets for new placer deposits in unglaciated areas include drainages such as Stewart, North Ladue and Yukon Rivers which lie outside of the pre-Reid glacial limit. Mineable placer deposits may also have formed on top of pre-Reid glacial drift and may be buried in valleys beneath Reid-age non-glacial alluvium. Prospective areas of this type are drainages which are near lode gold deposits in the Clear Creek area and in drainages near felsic volcanics in the Dawson Range. At the limits of both the Reid and McConnell glaciations, auriferous pre-glacial or interglacial gravel can often be buried by glacial and glaciofluvial deposits. Low-grade auriferous glaciofluvial gravel can also be derived form the reworking of pre-glacial gold-bearing gravel. Prospective areas for these types of placer deposits are the South McQuesten River valley and the creeks draining the Ruby Range on the east side of Kluane Lake. Within the McConnell glacial limits, placer deposits may be found in valleys oriented obliquely to the paleoflow direction of the glacial ice. Economic to sub-economic placers may also be found along meltwater channels within the McConnell ice limit. Prospective areas of this type of deposit are the drainages which lie to the north of Livingstone placer camp. The possibilities for new placer mining areas within glaciated areas must be investigated, and new placer gold reserves will undoubtedly be found within these areas. These potential gold deposits may be explored by techniques such as surficial mapping, airphoto interpretation and bulk sampling of potential gold-bearing units.

Geological map (1:50,000 scale) of "Dolores Creek" area, Wernecke Mountains, central Yukon (NTS 106C/14) including geological cross-sections and mineral occurrences.

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

Detailed exploration conducted during 2006 in the western part of the Skukum Creek deposit has revealed new structural, mineralogical and geochemical features. The deposit incorporates a number of (at least six or seven) sub- parallel narrow mineralized zones, coincident with andesite-dacite-rhyolite dyke swarms extending for at least 1 km along strike and for hundreds of metres down-dip. Various mineralized zones differ in size, structural setting, intensity and composition of mineralization, and, in total, form a large mineralized package more than 200 m wide, corresponding to a property- to district-scale fault zone extending for over 10 km and traced by a dyke belt. Significant potential exists for the exploration of these structures along strike and down-dip. The diamond drilling intersected numerous high-grade intercepts of gold and silver mineralization corresponding to the low-sulphidation sub-type of epithermal gold-silver deposits. However, strong enrichment in base metals (up to 25% of combined Zn+Pb+Cu) and arsenic suggests essential differences from typical epithermal mineralized systems.

The central Yukon Territory has a number of favourable placer deposit settings due to its unique history of multiple glaciations, active stream sedimentation in association with proglacial outwash settings and terrain which has remained unglaciated. Placer gold was found along the Stewart River on point bars in 1884 prior to the discovery of gold in the Klondike area. This was the first indication that the Yukon Territory contained important economic concentrations of placer gold. This study is concerned with the late Tertiary and Quaternary geology in the Lower Stewart River and adjacent Yukon River above Dawson. Previous systematic surficial geological mapping and testing for placer gold on the high-level terraces along these rivers has been limited. This report describes the sedimentology and stratigraphy of key gravelly exposures in this area because similar high-level terraces in the Fortymile River drainage in Alaska had been mined for gold for many years. Work of this type also provides information on the physical characteristics of gravelly deposits (e.g., grain size distribution) which may assist regulatory decisions on placer mining in the lower Stewart and Yukon drainages. Accompanying this report are two 1:50 000-scale surficial geology maps including marginal notes (Garner Creek, NTS 115O/13 and Matson Creek and Ogilvie NTS 115N/9 (east half) and 115O/12), as well as one 1:250 000-scale topographic map (Stewart River - NTS 115N/O) including field study site locations, heavy mineral sample sites and hardrock 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.

The southern Nash Creek area is located along the northern boundary of the Selwyn basin, and is underlain mainly by the Ediacaran–Cambrian Hyland Group, the Devonian–Mississippian Earn Group and the Mississippian Tsichu Group. Several Au and polymetallic mineral deposits are hosted by the Hyland Group and Paleozoic platformal carbonate rocks in the surrounding region. The southern Nash Creek area is bordered by regional-scale, southeast-striking thrust faults, which include the Dawson thrust to the northeast and the Robert Service thrust to the southwest. Based on stratigraphic relationships identified during 1:50 000-scale bedrock mapping, Hyland Group rocks in the area are considered to belong to the Cryogenian–Ediacaran Yusezyu Formation, the Ediacaran Algae Formation and the Ediacaran–Terreneuvian Narchilla Formation. Earn Group rocks include mainly shale and lesser amounts of interbedded dolostone, sandstone and shale. Tsichu Group rocks mostly comprise quartzite. The Yusezyu and Narchilla formations host (Paleozoic?) gabbro sills, and the Earn and Tsichu groups host gabbro sills that are considered to belong to the Triassic Galena suite. Rocks in the southern Nash Creek area exhibit a northeast-to-southwest dipping foliation that is axial planar to southeast-trending folds.