The Kalzas W-Sn-Mo deposit is located in central Yukon, 282 km north of Whitehorse on the northern side of Big Kalzas Lake. Wolframite-molybdenite-cassiterite mineralization occurs in sets of large planar quartz veins which cross-cut Selwyn Basin clastic rocks of the Upper proterozoic Windermere Supergroup, or "Grit" unit. The deposit has a concentric alteration halo with an outer sericite dominated zone, an inner "potassic' core and intense tourmalinization throughout the potassic zone and part of the sericite fringe. Intense fracture and quartz-tourmaline veinlet stockwords are present. No plutonic rocks are exposed in the local area though an underlying pluton is suspected. Kalzas has similarities to many wolframite deposits throughout the world, including those of southeast Asia which contain the bulk of world tungsten reserves. In contrast, North American tungsten mines having wolframite as the dominant tungsten phase are not as common as scheelite skarn deposits which produce most of our domestic tungsten.

Galena and pyrrhotite occur in manganese-stained quartz-carbonate breccia beneath rusty limestone. Surface geology of the area suggests that the mineralization is a replacement of brecciated limestone in the footwall of a low-angle fault. Results from previous exploration have proved disappointing but the host structure is probably regional in extent and larger deposits may exist along strike.

Wernecke breccia comprises numerous intrusive hematitic breccia zones exposed in the Wernecke and Ogilvie mountains of central Yukon. The breccias were emplaced in Middle Proterozoic time into Middle Proterozoic strata of Wernecke Supergroup, Fifteenmile group, and possibly Pinguicula group. Significant mineralization of Cu, U, Co, Ag and Au within and near breccia zones occurred during widespread Fe, CO2, and Si metasomatism. Following a period of hydrothermal activity and intense fracturing, breccia zones in the study area were generated in open spaces produced by extensional faulting or rapid expansion of volatile-rich fluids. A strong spatial correlation between breccia and crosscutting mafic to felsic intrusions indicates a magmatic linkage. Metasomatism extended from before brecciation to after cooling of the igneous intrusions. The metasomatising fluids may have been partly derived from residual liquids of possible tholeiitic magma chambers fractionating at depth. Regional deformation and metamorphism incurred during Racklan orogeny in Middle Proterozoic time preceded brecciation; the breccias developed in fully lithified rock. Previous models of breccia genesis invoking evaporite or mud diapirism are considered invalid.

The Boulevard gold prospect, located in the Independence Creek area of the Dawson Range, comprises sheeted, auriferous quartz-sulphide-carbonate veins and fault breccia, hosted mainly by mafic schist. The nearby Toni Tiger molybdenum showing is characterized by quartz-molybdenite veins cutting Late Permian meta-aplite and garnet-pyroxene skarn of uncertain age. We present geochronological evidence that gold and molybdenum were deposited at 96-95 Ma, approximately 3 m.y. after intrusion of the Dawson Range batholith and Coffee Creek granite. Fluid inclusions from mineralized quartz veins suggests that gold at Boulevard and molybdenite at Toni Tiger were formed from similar H2O-CO2-NaCl type fluids between 279 and 310°C and >1 kbar. We conclude that both are part of the same mineralizing system, and that structurally-hosted gold at the nearby Coffee deposit and in the Moosehorn Range of western Yukon may be broadly related, post-arc orogenic systems developed during exhumation of the Dawson Range in mid-Cretaceous time.

Tin and tungsten-bearing veins, breccias and skarns occur in a 60 km long belt trending west from Keno Hill to the Tintina Fault. They are hosted by mid-Cretaceous felsic intrusions, or adjacent metasedimentary rocks of Upper Precambrian to Mississippian age. Tin occurrences are mainly associated with two-mica granites in the southern part of the belt, while the tungsten lodes are more commonly associated with biotite-hornblende granitoids. Tin- and silver-bearing veins are associated with the central granite phase of a zoned intrusion in the northwest part of the belt (the Syenite Range). The zoned intrusion ranges in composition from tourmaline orbicular granite to granite to quartz monzonite to syenite. Most skarns are tungsten-dominant, whereas most breccias and veins are tin-bearing. The skarns are calcic and reduced. Three stages of skarn mineral formation and associated minerals are recognized:: 1) isochemical contact metamorphism, including diopside, grossular, wollastonite, and tremolite; 2) metasomatic skarn formation including andradite, idocrase, hedenbergite, axinite, and some sulphide minerals; and 3) retrograde alteration including actinolite, chlorite, clinozoisite, epidote, calcite, biotite, scheelite, cassiterite and sulphide minerals. Sulphide minerals are mostly minor, with pyrrhotite and pyrite predominant. Breccias, veins and sheeted veins of tin and tungsten occur in steeply diping tabular bodies close to felsic intrusions. The veins consist of quartz, tourmaline or chlorite. Tin-bearing veins and breccias contain all three gangue minerals plus pyrrhotite, pyrite, sphalerite, chalcopyrite, arsenopyrite and galena. Tungsten is only found in quartz (~orthoclase) veins which contain minor pyrite and molybdenite. Sheeted vein systems consist of three mineral assemblages:: 1)quartz-orthoclase-scheelite, 2) quartz-orthoclase-cassiterite, and 3) tourmaline-cassiterite. The first assemblage is present both in the endo- and exocontact of felsic intrusions, whereas the second and third occur further away from the granite in metasedimentary rocks which generally lie outside the thermal aureole of the intrusion. Breccia clasts consist of quartzite, schist, and/or vein fragments (quartz, tourmaline, or chlorite). The breccias are either clast-supported with a matrix of rock flour, or matrix-supported with a matrix (groundmass) of crystalline quartz, tourmaline or chlorite similar to vein material. Geochemical studies of the McQuesten River occurrences indicate that:: 1) Some properties are exclusively tin or tungsten properties, but others contain both metals. There is a positive correlation between tungsten and tin in some tin-bearing rocks. 2) Silver is common in veins and skarns which contain over 50 ppm Sn. 3) Gold occurs in significant quantities in most skarns and in several veins. 4) There is a positive correlation between gold and bismuth in the skarns. Bismuth can be used as a pathfinder for gold in these skarns.

A post-depositional hydrothermal alteration product in White Channel sediments and underlying bedrock is divided into 3 zones. These zones, termed the Bleached Zone, the Iron Zone, and the Footwall Zone, are characterized by the development of secondary clay minerals with moderate to high crystallinities. Trace element concentrations of Fe, Mn, As, Sb, Hg, Co, Ba and S are anomalously high in the Iron and Footwall zones. Three types of low temperature, post-metamorphic veins appear to be spatially related to both the distribution and intensity of alteration. Field relationships of altered and unaltered White Channel sediment show zoning patterns which cannot be explained by surface weathering and percolation of meteoric surface fluids. Economic implications of the alteration of White Channel alluvium are that there may be a hydrothermal style of gold mineralization, in addition to gold which was initially deposited in a placer environment. Testing and exploration of altered White Channel alluvium should be done with this in mind, particularly for extremely fine-grained gold which may accompany the alteration product.

A detailed evaluation of structure and alteration related to gold- and silver-rich, base metal-bearing veins was completed at the Skukum property as part of the 2002 mineral exploration program. The structural setting is an east-trending sinistral strike-slip system bounded by the Berney Creek and Goddell faults to the south and north, respectively. The deposit comprises northeast-trending quartz-sulphide mineral shear veins that formed during syn-tectonic intrusion of rhyolite and andesite dykes related to the Eocene Mount Skukum caldera complex. A genetic relationship between mineralization and certain rhyolite dykes is indicated by patterns of alteration and mineralization. Dilational, northeast-trending structures interconnect and splay off the controlling faults, and host extensional quartz-sulphide mineral veins. At Skukum Creek the main gold-silver-bearing minerals are electrum and freibergite, which precipitated with late galena-stibnite mineralization, whereas refractory gold in arsenopyrite is the main style at Goddell. A geological model is proposed that facilitates identification of prospective structures within the property.

During the summer of 1976, prospecting and mining exploration activity in the Wind-Bonnet Plume River area was concentrated on uranium-copper mineralization associated with breccia bodies in Lower Proterozoic rocks. As well, Geological Survey of Canada sponsored several projects in the area, including a geochemical survey and water, stream sediment and rock sampling. This report provides an overview of the geology and mineralization in the Wind-Bonnet Plume River Area.

The Bear Paw breccia zone is located at the Clear Creek property in the Tintina gold belt, central Yukon Territory. Gold mineralization occurs in hydrothermal breccias with stockwork quartz + potassium-feldspar + sulphide veins that overprint earlier intrusive and tectonic breccias. Grades of up to 2.3 g/t gold over 31.8 m have been intersected in recent drilling. The Bear Paw breccia zone is 1.5 km from any significant-sized granitoid stock and thus is indicative of the high potential for gold mineralization outboard of Tombstone Plutonic Suite stocks.

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