Kalzas, in central Yukon, is a porphyry-style stockwork and sheeted-vein wolframite deposit. Alteration includes a potassic core, a quartz-tourmaline-sericite zone and an outer quartz-sericite-pyrite zone, the latter in excess of 2 km in diameter. Wolframite is confined to the inner two zones, in an oval area 1500 m by 800 m. The wolframite is disseminated within the quartz-tourmaline stockwork and also occurs as coarse crystals in sheeted veins. Mineralization occurs within Neoproterozoic to Early Cambrian Hyland Group quartzites and phyllites, which are likely intruded at depth by a pluton, possibly of the Cretaceous Tombstone Suite. From 1981 to 1984, Union Carbide carried out mapping, soil and rock geochemistry, an airborne magnetometer survey, road building, trenching and drilling of two diamond drill holes. Results from Copper Ridge's 2001 sample program range from 0.3% WO3 to 0.5% WO3 over widths up to 70 m. They demonstrate the potential to define a signifi cant resource of surface-mineable tungsten mineralization at a grade of 0.4% WO3 or better. Drilling is required to confirm grade continuity at depth and along strike.

A sequence of Mississippian felsic volcanic rocks up to 600 m thick occurs in the St. Cyr Range of the Pelly Mountains. The volcanic rocks occur in a belt 80 km long and up to 25 km wide. This belt lies within the Pelly-Cassiar Platform which is bounded to the southwest by the Yukon Crystalline Terrane and to the northeast by the Selwyn Basin. Chemical analyses indicate that most of the volcanic rocks of the Seagull Creek volcanic belt are alkali rich and potassic. Silver, lead and zinc in the form of argentiferous galena and sphalerite and barium in barite constitute most of the mineralization associated with the volcanic rocks. Two main styles of mineralization occur:: stratabound-tpe and vein-type. A model of origin for the deposit is speculative, but at this preliminary stage, two classes of stratiform mineralization are proposed for this area, both related to exhalative centres. The first type is local (proximal) and consists of more massive and thicker layered sulphide units interbedded with the regional clastic and exhalite horizons. The second type of mineralization is regional (distal) in extent and consists of barite and chert horizons with minor to negligible amounts of disseminated and/or thinly layered sulphide.

The Logan (MINFILE 105B 099) and YP (MINFILE 105B 001) zinc-lead-silver deposits are located in the Rancheria District, Yukon Territory. These deposits and numerous other occurrences occur in veins and breccia zones which cut clastic sedimentary rocks of Proterozoic and Palaeozoic age, along fracture zones cross-cutting Cretaceous granites and Eocene volcanic dykes of mafic and felsic composition, and form replacement bodies in Palaeozoic carbonates. At the Logan and YP deposits, four phases of mineralization can be distinguished. The main sulphide minerals are sphalerite, galena, pyrrhotite, pyrite, chalcopyrite and arsenopyrite. Silver is mostly confined to galena, but also occurs in tennantite-freibergite group minerals, stannite, Pb-Ag-Bi-sulphosalts of the matildite-galena series and lillianite homologues. Arsenopyrite geothermometry using the method of Kretschmar and Scott (1976) returned maximum formation temperatures of 465° - 490° C at YP and 335° - 385°C at Logan. Microthermometric investigations of fluid inclusions in quartz associated with the YP mineralization showed formation pressures corresponding to a depth of 2500 m. Fluid inclusion data from quartz suggest that mineralization at YP and Logan is caused by a mixture of magmatic and metamorphic fluids. The fluid inclusions have low salinities of 34 weight per cent NaCl equivalent, an unusally low value for fluids which have separated from acid magmas. The metamorphic fuids may have been derived from metamorphic dewatering of Palaeozoic sediments.

Gold mineralization at the Mt. Skukum deposit occurs in nearly vertical quartz-carbonate veins which crosscut flat-lying andesites with a NNE trend. The mineralized veins represent the second stage of a two stage hydrothermal system, the first of which resulted in emplacement of thin chalcedonic veinlets. These two stages of veins are probably indicative of an evolving hydrothermal fluid rather than being representative of two separate events. Vein emplacement is one of the latest of a series of events which began with volcanism, producing felsic and andesitic volcanic rocks which overlie basement in this area. Subsequent periods of tectonism produced large faults along which rhyolitic dykes were emplaced. Continued tectonism resulted in reactivation of old faults along which andesitic and dacitic dykes were injected, crosscutting rhyolite dykes in many cases. As volcanic activity waned, the faults remained active, leaving zones of high permeability which acted as conduits for the still active hydrothermal circulation. Veins appear to have been emplaced at low temperature in a circulating hydrothermal system driven by a heat source at depth associated with dykes present in the area. Circulating hydrothermal fluids may have leached gold from the surrounding andesitic volcanics during propylitization. Permeability may have been controlled by faulting, brecciated flow tops and bottoms, and lapilli tuff horizons. Gold was precipitated in highly permeable conduits, such as the Main Fault Zone and breccia bodies.

Detailed vertical-face mapping of 'Slab Creek' was carried out in the summer of 2001 to evaluate the relations of Wernecke Breccia bodies with alteration, veining and iron oxide-copper-gold mineralization. Slab Creek is situated near the 'Slab' mineral occurrence in the Bonnet Plume River district of the Wernecke Mountains. Meta-sedimentary rocks in the area consist of meta-siltstone, meta-silty dolomite and phyllite of the lower succession of the Early Proterozoic Wernecke Supergroup, known as the Fairchild Lake Group. These rocks were folded and metamorphosed to lower greenschist facies, and were subsequently intruded by the Wernecke Breccias during the Mid Proterozoic. Three alteration zones can be recognized within Slab Creek, an inner feldspar zone coinciding with the large breccia bodies, surrounded by a chlorite-quartz-carbonate zone, grading outward into a sericite-chlorite zone. Alteration, veining and mineralization is most intense within the albite alteration zone where iron oxide-copper-gold (cobalt-uranium) mineralization is disseminated and occurs as vein infill.

From 2017-2019, framework metallogenic studies were completed in the eastern Yukon-Tanana upland in eastern Alaska. Numerous previously undated plutons known or suspected to contain components of porphyry, epithermal, and intrusion-related gold systems and associated deposit types were sampled for age and zircon trace element determinations between the Black Mountain area and the Yukon border, north of the Tanana River and south of the Yukon River. A collection of 54 samples were collected by Douglas Kreiner (USGS, Alaska Science Center). Zircon grains were separated from each sample. The samples were examined by U-Pb analysis by laser ablation-inductively coupled plasma mass spectrometry (LA-ICP-MS) in a USGS laboratory in Denver, CO. The samples contain evidence of several discrete periods of magmatic activity, with concordant zircon dates that range from ca. 53.3-2727 Ma. The bulk of analyzed samples are between ca. 68-72 Ma. Other specific periods of magmatism based on zircon dates range from ca. 55 Ma, ca. 100-112 Ma, ca. 130 Ma, and ca. 180-211 Ma. The ca. 340-365 Ma dates are likely inherited from host rocks that were previously unidentified in the field area but are known in the regional framework geology. Archean and Proterozoic zircon dates are not common, but likely represent inheritance from sedimentary and metasedimentary protoliths from the region.

From 2017-2019, framework metallogenic studies were completed in the eastern Yukon-Tanana upland in eastern Alaska. Numerous previously undated plutons known or suspected to contain components of porphyry, epithermal, and intrusion-related gold systems and associated deposit types were sampled for age and zircon trace element determinations between the Black Mountain area and the Yukon border, north of the Tanana River and south of the Yukon River. A collection of 54 samples were collected by Douglas Kreiner (USGS, Alaska Science Center). Zircon grains were separated from each sample. The samples were examined by U-Pb analysis by laser ablation-inductively coupled plasma mass spectrometry (LA-ICP-MS) in a USGS laboratory in Denver, CO. The samples contain evidence of several discrete periods of magmatic activity, with concordant zircon dates that range from ca. 53.3-2727 Ma. The bulk of analyzed samples are between ca. 68-72 Ma. Other specific periods of magmatism based on zircon dates range from ca. 55 Ma, ca. 100-112 Ma, ca. 130 Ma, and ca. 180-211 Ma. The ca. 340-365 Ma dates are likely inherited from host rocks that were previously unidentified in the field area but are known in the regional framework geology. Archean and Proterozoic zircon dates are not common, but likely represent inheritance from sedimentary and metasedimentary protoliths from the region.

Meta-sandstone, siltstone and phyllite, with marble and intermediate-to-felsic tuffaceous horizons, host the Munson (TBMB) and Mod zinc-lead occurrences, about 7 km southwest of the Dan and Crescent properties. These host rocks are part of the Late Devonian Dorsey assemblage. Complexities resulting from isoclinal folding and faulting inhibit direct correlation of strata from one ridge exposure to another. The strata are overlain by dark meta-siltstone of the mid-Mississippian Swift River succession. Although faulted, the lack of a strong lithologic contrast between the units suggests only minor dislocation. Pre-Jurassic and Cretaceous granites and a diorite sill intrude the Dorsey rocks. Chloritic tuffaceous layers host showings of pyrrhotite, chalcopyrite and sphalerite; carbonate pods contain sphalerite + galena ± pyrrhotite; and quartz-feldspar meta-tuff layers are pyritic. U-Pb zircon age results for leucosome from a nearby exposure of lower Dorsey rocks indicate an approximate crystallization age of 373 Ma, and about 358 Ma for a granitic dyke in the upper Dorsey assemblage, bracketing the age of deposition of this Yukon-Tanana Terrane assemblage.

Marble, calc-silicate rock and pelitic layers of the Ram Creek assemblage surrounding the Dan Zn (± Cu-Pb-Ag) occurrence display ample evidence of a monocyclic structural evolution with three main events of progressive deformation (D1-D3). These events developed a tightly folded package of west-northwest-trending tectonites. Primary planar structures (S0) generally lie sub-parallel to two tectonic foliations (S1 and S2), which dip shallowly to steeply southwest. Inter-foliation slip (D3) resulted in a transverse, sub-vertical foliation (S3) that dips generally shallowly to moderately north. Cross-sections based on new mapping and fold analysis indicate that similar folds containing stratabound zinc-sulphide mineralization should be present south of the Dan occurrence, as part of regional north-northeast-verging folds or a thrust-fault-repeated succession.

Quantitative mineralogy, U-Pb geochronology of zircon and monazite, 40Ar/39Ar geochronology of muscovite and sericite, and Pb isotopes from galena in veins and feldspar in plutons provide insight into the age of metamorphism, mineralization, intrusion emplacement and the sources of metals at the Plateau South (MINFILE 105N 034, 035, 036) occurrences in central Yukon. Orogenic mineralization and metamorphism is ca. 110 Ma to 100 Ma, and possibly as old as ca. 130 Ma. Following deformation and regional metamorphism, two biotite-muscovite plutons, the Russell stock and Armstrong pluton, were emplaced at 95.39 ± 0.03 Ma and 95.51 ± 0.03 Ma, respectively. These plutons are here reassigned to the Tungsten suite based on mineralogy, chemistry and age. Coeval with these plutons are contact metamorphism and possibly intrusion-related mineralization. Lead isotopic data from galena cluster into two groups: Group 1 is enriched in thorogenic Pb with 206Pb/204Pb values between 18.31 and 18.14, 207Pb/204Pb between 15.62 and 15.55 and 208Pb/204Pb between 38.77 and 38.30. Group 2 is isotopically evolved with 206Pb/204Pb values between 19.13 nd 18.91, 207Pb/204Pb between 15.78 and 15.63 and 208Pb/204Pb between 39.24 and 39.07. We suggest that late Early Cretaceous mineralization is related to large-scale orogenic fluids that tapped primitive (deep?) metal sources and early Late Cretaceous mineralization, coeval with local intrusions, sourced isotopically distinct metals from the intrusions. Alternatively, all mineralization could relate to Early Cretaceous orogenic fluids but with heterogeneous, locally derived metal sources and thermal resetting of Ar ages near the intrusions.