The Irvine Lake and Gravel lake map-areas (NTS 105B/10,11) lie within the northern Omineca Belt, west of the Tintina-Northern Rocky Mountain Trench (NRMT) fault. The eastern part of the area is underlain by Proterozoic to early Paleozoic metasedimentary rocks of Cassiar terrane, a fragment of the North American miogeocline which has been displaced northward on the Tintina-NRTM fault. The western part of the area is underlain by basaltic metavolcanics, serpentinized ultramafic rocks, metagabbro, and cherty and calcareous metasediments of the Slide Mountain terrane. Unfoliated to weakly foliated granitic intrusives (Marker Lake and Cassiar batholiths and Cabin Creek and Gravel Creek stocks) occur throughout the area intruding both the Cassiar and Slide Mountain terranes. Slide Mountain and Cassiar terranes are juxtaposed by an east-verging thrust referred to in this area as the Zak fault. Southwest of Irvine Lake, the thrust places serpentine, basaltic meta-volcanics, and an undeformed dioritic intrusion onto a footwall consisting of the Proterozoic Tsaydiz Formation and older units. Northwest of Irvine Lake, near Shootamook Creek, the thrust places cherty metasediments of the allochthon onto marble and quartzite inferred to be lower Cambrian Rosella and Boya Formations, respectively. The northern end of the Cassiar batholith extends into the southwestern corner of Irvine Lake map area. Its northeastern contact with rocks of Slide Mountain terrane is a subvertical, northwest-southeast trending mylonite zone several tens of metres wide. Mesoscopic structures including S-C fabrics and shear bands prove dextral displacement parallel to a variably plunging, but commonly sub-horizontal stretching lineation. The mylonite zone lies along a pronounced topographic lineamnet which extends from the trace of the Cassiar fault south of the Alaska Highway northwestwardly into the Irvine Lake map-area rather than veering to the west as previously mapped. Mineral occurrences in this area are primarily near the contact of granitic intrusions and carbonate rocks. Carbonate rocks hosting the deposits belong to the upper Proterozoic Ingenika Group (Swannell, Tsaydiz and Espee formations) rather than the Lower Cambrian Atan Group as has been inferred for nearby deposits in the Rancheria district. Other, non-carbonate-hosted mineral occurrences include a porphyry Mo prospect and Ag, Pb, Zn veins.

The study area provides a clear record of the Proterozoic geological evolution of northern and central Yukon Territory. The area lies in the Wernecke Mountains of east-central Yukon, approximately 150 km north-northeast of the town of Mayo, and 20 km west of the Yukon-Northwest Territories border. The rocks record events of sedimentation, magmatism and deformation ranging in age from Early Proterozoic to Tertiary. Rocks of Early Proterozoic age predominate, but strata of Middle Proterozoic, Late Proterozoic, and Early Paleozoic ages are also abundant.

not_specified

Geology of Thirty-Seven Mile Creek map area (1:50,000 scale), southern Yukon Territory (NTS 105D/13) including geological cross sections and mineral occurrences.

Geology including geological cross sections and mineral occurrences.

Metasedimentary and meta-igneous rocks in ‘Mendocina Creek’ (NTS 105F/5) and eastern Livingstone Creek (NTS 105E/8) areas are part of three distinct stratigraphic sequences: from east to west, the Sheep Creek, Scurvy Creek and Dycer Creek successions. The Sheep Creek succession contains extensive carbonate horizons and is likely part of the Cassiar terrane. To the west, metaclastic rocks of the Scurvy Creek succession are extensively intruded by sills and dykes composed of augen meta-granite of Early Mississippian age; they are correlated with the Snowcap assemblage of Yukon-Tanana terrane. The overlying Dycer Creek succession in the southwest comprises marble, carbonaceous rocks, greenstone and quartzite of Lower Mississippian (and younger?) age that probably correlate with the Finlayson assemblage of Yukon-Tanana terrane. The ‘Mendocina Creek’ area experienced at least four phases of deformation and greenschist- to amphibolite-facies metamorphism. An east-verging thrust locally imbricates the Scurvy Creek succession and the boundary between the Yukon-Tanana and Cassiar terranes corresponds with a west-verging, brittle-ductile thrust fault in the eastern part of the area. Re-interpretation of the geology in western Quiet Lake map-area indicates that this boundary is located 20 km east of the d’Abbadie fault, the previously inferred terrane boundary.

not_specified

not_specified

Clear Creek map area of central Yukon is underlain by deformed and metamorphosed Proterozoic and Paleozoic rocks of western Selwyn Basin (Hyland Group, unnamed carbonate unit, Road River and Earn groups) and mid-Cretaceous felsic intrusions. Metasedimentary rocks are disposed in a warped northwest to northeast-dipping structural panel with younger, structurally shallow rocks in the north and older, structurally deeper rocks in the south. Younger rocks in the north are deformed into Lost Horses syncline, a southwest-overturned tight to isoclinal syncline with an axial surface trace extending across the northern part of the area. Older rocks at deeper structural levels in the south are deformed by a suite of fabric elements that probably post-date Lost Horses syncline, indicate a top-to-the-northwest sense of tectonic transport, and are probably related to Early Cretaceous displacement on the Tombstone thrust. Subsequent deformation warped the panel into its current orientation. All structures are intruded by mid-Cretaceous felsic intrusions including hornblende-biotite (rare muscovite) granite, quartz monzonite, granodiorite, syenite, and quartz syenite. Mineral occurrences are mainly precious metal, tin, and/or tungsten bearing vein, skarn, and breccias associated with felsic intrusions. Bedded barite occurs in Earn Group strata. New analyses of mineralized samples confirm earlier data reporting significant gold values in veins cutting felsic intrusions and nearby country rock, and correlation of anomalous gold with anomalous bismuth in some veins.

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.