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TitleCoal River (NTS 95D): a new bedrock geology map in southeast Yukon
AuthorPigage, L; Abbott, G; Roots, C
SourceCordilleran Geology and Exploration Round-up, abstracts volume; by Association for Mineral Exploration BC; 2011.
Alt SeriesEarth Sciences Sector, Contribution Series 20090285
MeetingMineral Exploration Roundup 2011; Vancouver; CA; January 24-27, 2011
Maps1 map
Map Info.geological, bedrock geology, 1:250,000
ProjectionUniversal Transverse Mercator Projection, zone 9 (NAD83)
RelatedThis publication is related to Pigage, L C; Abbott, J G; Roots, C F; Association for Mineral Exploration BC; Association for Mineral Exploration BC; Association for Mineral Exploration BC; (2011). Bedrock geology of Coal River map area (NTS 95D), Yukon (1:250 000 scale), Yukon Geological Survey Open File 2011-1
ProvinceYukon; Northwest Territories
AreaCoal River; Rock River; Smith River; Mount Skonseng; Last Mountain; Mount Kostiuk; Gusty Lakes; Lootz Lake
Lat/Long WENS-128.0000 -126.0000 61.0000 60.0000
Subjectsstratigraphy; structural geology; geophysics; geochemistry; lithology; stratigraphic correlations; stratigraphic analyses; structural features; faults; folds; bedrock geology; magnetic surveys, airborne; Eocene; Paleocene; Grayling Formation; Toad Formation; Fantasque Formation; Mattson Formation; Besa River Formation; Road River Group; Nonda Formation; Muncho Formation; McConnell Formation; Stone Formation; Dunedin Formation; Sunblood Formation; Rabbitkettle Formation; Otter Creek Formation; Crow Formation; Hyland Group; Vampire Formation; Narchilla Formation; Yusezyu Formation; Toobally Formation; Tertiary; Triassic; Permian; Mississippian; Devonian; Silurian; Ordovician; Cambrian; Proterozoic; Cretaceous
Illustrationssketch maps; geochemical analyses
ProgramBase Metals - South central Yukon (Selwyn Basin), GEM: Geo-mapping for Energy and Minerals
AbstractThe Coal River (NTS 95D) accelerated mapping project is jointly funded by the Geological Survey of Canada Geomapping for Energy and Minerals program (GEM) and the Yukon Geological Survey. It provides a modern framework bedrock geology map and a new surficial map by building on recently completed mapping by the Yukon Geological Survey. Field work extended for approximately 5 weeks during summer 2009 with a core team of 3 bedrock geologists and 1 surficial geologist.

Coal River map area is located in southeast Yukon at the south margin of Selwyn Basin and the southeast end of the Tintina Gold Belt. These affinities indicate that the area has high mineral potential but it is under-explored due to extensive forest cover restricting helicopter access, lack of roads, less than 10% bedrock exposure and old framework geology maps.

Strata range from Proterozoic to Eocene in age and are divided into six successions. The oldest succession is the Neoproterozoic-Cambrian siliciclastic sediments, consisting of Hyland (Yusezu Fm, Narchilla Fm) Group, Vampire Fm and Sekwi Fm-correlative rocks. We were unable to consistently differentiate between these units because of their lithologic similarities. Succession 2 unconformably overlies this first succession and consists of a widespread basal upper Cambrian-lower Ordovician carbonate conformably overlain by Rabbitkettle Fm limestones in the west and Crow Fm coarse siliciclastic sediments in the east. These formations outline an east-west facies transition from shallow water clastic sedimentation near a paleogeographic high at the eastern edge of the area to relatively deep water silty limestone deposition to the west. The lower to middle Ordovician Sunblood Fm carbonate constitutes the third succession and was deposited upon a shallow platform that extended across the eastern 2/3 of the map area. Silurian?-Middle Devonian carbonates of Macdonald Platform undergo a northward facies change to black marine shales of the Road River Gp in Selwyn Basin. Middle Devonian to Triassic Besa River, Mattson, Fantasque and Grayling -Toad formations record transgressive and regressive clastic cycles. A post-orogenic extensional half graben along the Rock River preserved Eocene fluvial mudstone, silt and sand with coal seams.

Submarine alkali basaltic volcanic rocks occur in at least two stratigraphic horizons in the first two successions. The basalts are interpreted as being rift-related

Nine small, previously ummapped granitic stocks were found in the northern and central portions of the map area, bringing the total number of known intrusions to 15. Immediately to the north, areally extensive plutons have been variously assigned to the Tay River, Tombstone and Tungsten suites. Unlike those to the north, most intrusions within Coal River map area are very magnetic and coincide with intense positive aeromagnetic anomalies. We suggest that many other magnetic anomalies in the map area are also associated with buried or unmapped intrusions because the hosting sedimentary rocks of the region have uniform low magnetic susceptibility.

Strata-bound and intrusion-related mineralization is documented by several mineral occurrences in both the Yukon and NWT parts of Coal River map area. Carbonaceous shales assigned to the Narchilla Formation have extensive ferricrete related to weathered pyrite-quartz interbeds in the Irons Creek drainage. MEL is a barite-sphalerite-galena-bearing, epigenetic MVT or Irish-type occurrence within Cambrian-Ordovician carbonate; several showings within 10 km to the northeast have similar mineralization. The Mattson Formation contains the Last Mountain bedded barite occurrence. Prospects for intrusion-related mineralization are considered to be high because the intrusions are barely unroofed and many intrude thick successions of limestone and dolostone. The Macmillan Pb-Zn-Ag replacement deposit and Hyland Gold Au occurrence are inferred to be associated with buried intrusions. Placer Au occurrences spatially associated with intrusions are located on both sides of the northern boundary of the map area. W skarns are common north of the map area.