The Brewery Creek gold mine (13.3 Mt @ 1.44 g/t Au) is a bulk tonnage, heap leach operation located 57 km east of Dawson City, Yukon. The deposit lies on the northeastern side of the Tintina Fault and within Selwyn Basin. Gold mineralization is hosted by intrusions of the mid-Cretaceous Tombstone Plutonic Suite (TPS), and Silurian to Carboniferous clastic metasedimentary rocks of the Steel Formation and Earn Group. The sedimentary rocks are faulted and variably folded, however they display poor cleavage development. The TPS intrusions are also faulted and contain rafts of argillaceous sedimentary rock. No regional ductile fabrics were observed to crosscut the intrusions. Five phases of intrusion have been recognized; these are `raft monzonite, feldspar porphyry (FP1), biotite monzonite, a second phase of feldspar porphyry (FP2), and a pyroxenite. The most important feature at Brewery Creek is a linear zone of monzonite intrusions, faulting and mineralization termed the Reserve trend. This zone trends west-northwest and has a moderate dip to the south. A number of stages and orientations of faulting have been identified along the Reserve trend; lithological relationships suggest a substantial amount of vertical movement occurred post-TPS emplacement and pre- to syn-mineralization.

The Brewery Creek mine is a bulk tonnage gold deposit located 57 km east of Dawson City, in central Yukon, within the foothills of the Ogilvie Mountains along the northeastern boundary of the Tintina Trench. High-level fracture-controlled gold mineralization is hosted within Cretaceous monzonite sills and Devonian Earn Group siliciclastic rocks of the Selwyn Basin. Structural controls include northeast and southeast sub-vertical shears bounded by moderately south-dipping, southeasterly-extending listric normal faults; listric faulting and sill emplacements are localized along pre-existing graphitic thrust faults. Gold occurs as sub-micron particles in solid solution with pyrite and arsenopyrite as growth bands around larger sulphide grains that are disseminated within fine quartz veinlets. The open-pit heap leach operation produces 75,000 - 80,000 ounces annually, with a stripping ratio of 1.5:1 and a cash cost of US$200/oz or less. The mineable reserves at the end of 1997 stood at 13.3 MT @ 1.44 gpt (613,000 oz).

not_specified

Auriferous sheeted quartz veins and silicified shear zones occur along the margins and within adjacent hornfels zones of mid-Cretaceous Tombstone intrusions near the head of Clear Creek in the central Yukon. The lodes are the source for more than 120,000 ounces of downstream placer gold production. These lodes contain variable amounts pyrrhotite, pyrite, and arsenopyrite, with less abundant scheelite - alkali-feldspar, muscovite, biotite and tourmaline are common gangue phases. Grab samples of mineralization often contain gold grades in excess of 1 ounce per ton. Gold-to-silver ratios vary most commonly from 1:1 to 5:1. Gold-rich quartz veins cut all stocks, adjacent hornfels and associated lamprophyre dykes commonly contain greater than 1% arsenic. Bismuth, and less consistently tungsten and stibnite, characterize many of the most highly mineralized veins within and surrounding the stocks. Quartz veins along the intrusive-metasedimentary rock contact around the Pukelman stock are also enriched in lead and silver. R-mode factor analysis of multi-element geochemical data for 111 gold- and sulphide-bearing rock samples indicates that there are two geochemically distinct metal suites in the Clear Creek occurrences. The first is characterized by As-Au-Bi ± Sb, Te ore-related mineral association, which is typical of many intrusion-related deposits in the Tombstone gold belt. Less consistently, anomalous concentrations of Ag, Co, Cu, Fe, and Mo occur within these auriferous rocks. The second metal factor is defined by Ag-Bi-Pb ± As, Au and Te. It characterizes metalliferous vein samples that have uncommonly low Au: Ag ratios and may represent a second hydrothermal episode. Tungsten shows little consistent correlation with the metalliferous veins in either element suite.

for a copy of this paper please contact the Yukon Geological Survey; geology@gov.yk.ca.

not_specified

not_specified

This report releases whole-rock geochemical assay results of 102 samples collected by the Geological Survey of Canada (GSC) and Yukon Geological Survey (YGS) from four Carlin-type gold zones (Conrad, Sunrise, Osiris and Anubis) in the Nadaleen Trend, Yukon.

Placer gold in the Clear Creek drainage basin is found in a variety of gravel deposits, each of which is associated with a specific geological setting. The schematic profile of Clear Creek drainage basin illustrates the distribution of these gravel deposits, and indicates both known deposits and favourable sedimentologic conditions for placer mineral accumulation. Known placer gold deposits include creek and gulch placers, as well as preglacial fluvial gravel or buried channels. Favourable placer deposit settings include alluvial fans, gravelly sediments similar to the Pliocene (?) White Channel gravel of the Klondike area, and specific glacially derived sediments. This paper describes each of the above placer deposit settings, and outlines the associated stratigraphy and sedimentology of placer gold deposits.

Map and report listing information on 419 mineral ocurrences in Yukon that contain noteworthy amounts of gold and/or silver. A capsule description of the occurrence's geology is present along with a list of the significant ore minerals. This is followed by information on the metal content of the occurrence and extent of exploration and development work. Accompanying this report is a 1:2,000,000-scale map of gold-silver deposits and occurrences in the Yukon Territory.