Deconstructing complex Au-Ag-Cu mineralization, Sonora Gulch project, Dawson Range: A Late Cretaceous evolution to the epithermal environment
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We present new field and U-Pb analytical data from the Sonora Gulch Project that demonstrate a protracted history of polymetallic mineralization (Au-Ag-Cu-Zn ± Mo) associated with several pulses of Cretaceous magmatism. Recent exploration on the Sonora Gulch Project has highlighted the presence of two important mineralized zones: the Nightmusic zone, a mesothermal Au-enriched base metal skarn, and the Amadeus zone, an epithermal Au-Ag system. Four U-Pb age dates determined from each of two feldspar porphyry dykes (ca. 74 Ma), a weakly mineralized quartz porphyry stock (ca. 75 Ma) within the Nightmusic zone and the Au-Ag mineralized Amadeus stock (ca. 75 Ma), demonstrate the widespread occurrence of Late Cretaceous magmatism. The age determinations indicate that mineralization occurring within the Sonora Gulch project area are temporally equivalent to the Casino Cu-Au-Mo deposit, located roughly 40 km to the west-northwest. These new data extend the currently known eastern limit of Late Cretaceous magmatism and associated mineralization.
New data on the geology and mineralization of the Skukum Creek gold-silver deposit, southern Yukon (NTS 105D/3).
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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.
Geology, mineralization and sampling results from the Kalzas tungsten property, central Yukon
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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.
Windy McKinley terrane, Stevenson Ridge area (115JK), western Yukon: composition and proposed correlations, with implications for mineral potential.
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Recent mapping in the ‘Windy McKinley’ terrane of Stevenson Ridge area of western Yukon defined two subdivisions of the terrane, an imbricated ophiolite and a succession of predominantly fine-grained, variably carbonaceous and calcareous clastic rocks extensively intruded by Middle Triassic gabbro. Further work in 2007 has revealed a third subdivision of felsic metavolcanic and carbonaceous clastic rocks, also spatially associated with voluminous gabbro. The two subdivisions of the terrane containing gabbro are reminiscent of the two subdivisions of the Delta district of Alaska, and gabbroic rocks from the two areas are coeval and geochemically similar. If the Stevenson Ridge successions correlate with those of the Alaska Range, the mineral potential of the Stevenson Ridge area would be appropriately increased.
Volcanic-associated massive sulphide (VMS) mineralization in the Yukon-Tanana Terrane and coeval strata of the North American miogeocline, in the Yukon and adjacent areas
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Discovery of the volcanic-associated massive sulphide (VMS) Kudz Ze Kayah (KZK) deposit in 1994, closelyfollowed by the discovery of the Wolverine VMS deposit, resulted in a period of intense exploration activity in Yukon. This led to the discovery of additional VMS mineralization that includes GP4F, Ice and significant new reserves at Fyre Lake. Numerous VMS prospects were identified. The Fyre Lake, KZK, GP4F, Wolverine, and Ice VMS deposits are hosted by the Yukon-Tanana Terrane (YTT) in the Finlayson Lake district of southeastern Yukon. The Fyre Lake deposit (8 200 000 tonnes of 2.1% Cu and 0.73 g/t Au) is stratigraphically lowest and occurs in mafic metavolcanic rocks of the Devonian to Mississippian Grass Lakes succession. The KZK and GP4F deposits (13 000 000 tonnes of 5.5% Zn, 1% Cu, 1.3% Pb, 125 g/t Ag and 1.2 g/t Au and 1 500 000 tonnes of 6.4% Zn, 3.1% Pb, 0.1% Cu, 89.7 g/t Ag and 2.0 g/t Au, respectively) are within the Devonian to Mississippian succession but lie stratigraphically above Fyre Lake in felsic metavolcanic rocks. The Wolverine deposit (6 237 000 tonnes of 12.66% Zn, 1.33% Cu, 1.55% Pb, 370.9 g/t Ag and 1.76 g/t Au) is hosted by Carboniferous rhyolitic metavolcanic rocks and carbonaceous argillite of the Wolverine succession. The Ice deposit (4 561 863 tonnes of 1.48% Cu ) occurs highest in the stratigraphy and is hosted within late Palaeozoic mafic metavolcanic and associated metasedimentary rocks of the Campbell Range succession. The YTT underlies a large part of Yukon, east-central Alaska and parts of British Columbia. VMS mineralization occurs within rocks of the YTT in the Dawson and Glenlyon areas of Yukon, in the Teslin-Rancheria area in Yukon and adjacent British Columbia, and in several areas within Alaska, as well as in the Finlayson Lake area of the Yukon. In the Dawson area, which lays adjacent to the massive-sulphide-rich Finlayson Lake district (before approximately 425 km of right lateral movement on the Tintina Fault), VMS prospects are hosted in Late Devonian to mid-Mississippian Nasina Assemblage and Permian Klondike Schist. In the Glenlyon area, massive sulphide mineralization and chert horizons occur within a belt of rocks that is at least 20 km long. In the Teslin-Rancheria area and adjacent northern British Columbia, several VMS prospects have been identified. The Alaskan VMS occurrences are in the Delta, Bonnifield and Trident Glacier districts. Exploration during this period was not confined to the YTT but extended into rocks of the North American miogeocline that are coeval, and possibly correlative, with Devono-Mississippian strata of the YTT. This led to the discovery of additional resources at the Marg and Wolf VMS deposits. The Marg deposit (5 527 002 tonnes of 1.76% Cu, 2.46% Pb, 4.60% Zn, 62.7 g/t Ag and 1.0 g/t Au) occurs in the Selwyn Basin within a Devonian to Mississippian sequence of carbonaceous siliceous phyllite, quartz-muscovite and quartz-chlorite phyllite and massive quartzite. These strata also host the Jane prospect. The Wolf deposit (4.1 million tonnes of 6.2% Zn, 1.8% Pb and 84 g/t Ag) occurs in the Pelly-Cassiar Platform within the Devono-Mississippian Pelly Mountains volcanic belt and is hosted by felsic metavolcanic and associated metasedimentary rocks. Numerous other VMS prospects, including MM, occur throughout the length of this 80-km-long volcanic belt. The newly defined VMS deposits are comparable in size to the average Canadian VMS deposit indicating the discoveries are significant. Mineralization in the YTT occurs in Late Devonian to Permian strata thus there are several prospective horizons and the potential for additional discoveries is significant.
A structural analysis of the upper Swift River area (105 B/3), Yukon, Part I: Dan Zn occurrence and implications for sulphide mineralization
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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.
Geology of the Main Zone at Mt. Skukum, Wheaton River area, southern Yukon
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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.