The Mitchell-Sheba occurrence is a gold, silver and base metal-bearing quartz vein system contained within a thrust slice of mafic schist that forms part of the Klondike Schist. The vein system formed late in the D4 folding event or subsequently thereafter. Mineralization occurs as gold + silver, base metal sulphides and sulphosalts within quartz veins. Low-grade gold associated with pyrite mineralization is hosted within the surrounding chlorite schist. The mafic rocks are interpreted to be metavolcanic in origin and have reached upper greenschist facies metamorphism. Hydrothermal sericite-carbonate alteration of the host rocks is associated with mineralization and is reflected in the whole rock geochemistry. The prospect underlies one of the larger soil geochemical anomalies in the Klondike region.

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.

La Teko Resources Ltd. acquired the Scheelite Dome gold property from Kennecott Canada Exploration Inc. in 1998. Kennecott had explored the central Yukon property since 1994. The strongly deformed Yusezyu Formation of the Upper Proterozoic-Lower Cambrian Hyland Group underlies the property and is intruded by unfoliated mid-Cretaceous granitic stocks, dykes and sills of the Tombstone Plutonic Suite (TPS). Vein-type (both metasediment- and granite-hosted), skarn and replacement mineralization on the property is associated with the TPS intrusives. Mapping, trenching and drilling by Kennecott identified numerous structurally controlled metasediment-hosted zones of mineralization within an east-west 3.5 km by 1.4 km > 40 ppb, gold soil anomaly. In 1997, a 13 hole 1052 m reverse circulation drill program tested the gold soil anomaly with the two best holes returning weighted averages of 0.48 g/t gold over 29 m (RC97-4) and 0.41 g/t gold over 61 m (RC97-11). In 1998, a seven hole 1268 m diamond drill program by La Teko tested targets defined using a combination of soil and rock gold anomalies, geological structures and chargeability and resistivity anomalies. Results included intersections of 1.04 g/t gold over 14.9 m, 1.07 g/t gold over 12.1 m, and 3.67 g/t gold over 7.7 m.

The term "Klondike Schist" describes metamorphosed igneous and sedimentary rocks first described from the Klondike area and later from south central Yukon. This paper describes the geology and chemistry of selected iron and base metal occurrences in Klondike Schist and proposes a model to assist further exploration for and evaluation of this type of mineralization. Four mineralized occurrences were examined in 1978, three on the northeast side of Tintina Fault in the Pelly Mountains - Fire Lake, North Lakes and Wolverine Lake and one southwest of the Tintina Fault, the Boundary prospect west of Dawson.

The study area is centred on the 91.2 ± 0.9 Ma Scheelite Dome quartz-monzonite stock of the Tombstone Plutonic Suite (TPS). This stock and associated dykes and sills intrude highly deformed metasedimentary strata of the Yusezyu Formation of the Neoproterozoic to Lower Cambrian Hyland Group. The emplacement of TPS intrusions post-dates regional greenschist-facies metamorphism and multiple phases of ductile deformation related to the Tombstone strain zone. Although the Scheelite Dome stock hosts auriferous, sheeted quartz veins, extensive soil geochemistry indicates that the bulk of the gold resource is hosted in the variably hornfelsed metasedimentary rocks immediately south of the stock. The associated gold-in-soil anomaly forms an east-trending corridor of anomalous gold values (>80 ppb) approximately 6 km long by 1.5 km wide, with a more weakly defined eastern continuation. Where metasedimentary bedrock is exposed in the corridor, gold is hosted in fault-vein arrays, and less commonly as disseminated grains and in replacement zones. The styles and distribution of mineralization are largely controlled by brittle structures; a phase of east-west shortening was largely coeval with gold mineralization. R-mode factor analysis of multi-element geochemical data indicates two geochemically distinct metal suites within the area of the gold-in-soil anomaly at Scheelite Dome. The first suite, characterized by Au-Te-Bi ± W ± As, possesses the stronger gold association and is typical of intrusion-related gold occurrences elsewhere in the Tombstone gold belt. The second suite displays a metal association of Ag-Pb-Zn-Cd-Sb ± Cu ± Au, which is more characteristic of mid-Cretaceous Ag-Pb-Zn mineralization in the Keno Hill district, located approximately 60 km to the east-northeast. Field observations, combined with soil geochemistry, suggest that the different metal associations are paragenetically related. However, the possibility of two distinct hydrothermal events cannot yet be ruled out.

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.

The Myschka property overlies a large mineralized area within and adjacent to a 1200 m by 600 m Cretaceous Tombstone Suite granodioritic intrusion. Mineralization is controlled by at least four wide east-west-trending lensoid zones of faulting, brecciation and hydrothermal alteration. Just north of the intrusion, the zones were followed for a distance of 1500 m; widths of individual zones vary from 20 to 100 m. The zones tend to coalesce into much wider (up to 200 m) brecciated packages that dip steeply (70-85°) to the south and apparently crosscut the intrusive. A network of northerly dipping fault and alteration zones crosscut these breccias. The breccias include intensive quartz stockwork and thicker quartz-filled shear zones containing disseminated gold-bearing sulphide (pyrite, arsenopyrite) mineralization. Rock samples returned numerous strongly anomalous gold values ranging from 200 ppb to 1.05 g/t throughout the extent of the breccia zones. Larger quartz veins locally exhibit much stronger sulphide enrichment, resulting in higher Ag, Bi, Sb, Pb, Zn and Cu values influencing property-scale geochemical zonation. A distinctive gold and pathfinder element soil anomaly is coincident with the breccia packages. During the 2002 exploration program, the prospect was advanced to drill-ready stage. Proposed drilling will test subsurface continuation of gold-bearing fault/breccia and alteration zones into the intrusive rock.

We have determined the major and trace element composition of approximately 2700 gold particles from 21 gold-bearing mesothermal quartz veins and 35 placer gold samples from the Klondike District in western Yukon Territory. Measured Au, Ag, Cu, and Hg contents were used to define a characteristic geochemical signature for each of the vein samples. These signatures were then compared with the various compositional populations that we have distinguished within each of the placer samples. Preliminary conclusions derived from the study include: 1) placer gold in both recent stream deposits and in the Plio-Pleistocene White Channel Gravels is detrital in origin; 2) the placer gold is mainly, if not entirely, derived from mesothermal quartz veins; 3) all lode sources for the placer gold have not yet been located; and 4) composition data can be used to link placer gold to its specific lode source.

Description and analysis of the geology of quartz veins containing gold ores in the Yukon Territory.