Abstract: The Keno Hill-Galena Hill mining district of central Yukon has been a prolific silver-lead-zinc producer since the early part of the century. Typical orebodies are extensive vein systems with a mineralogy consisting of siderite, quartz, pyrite, galena, sphalerite, and freibergite in varying combinations. The veins are restricted to steep SE-dipping fault zones principally contained within a brittle graphitic quartzite unit and some concordant greenstone bodies. The main silver lodes form a narrow east-west belt, 25 km long, and have been assigned a mid-Cretaceous age as have nearby granitic bodies and their associated tin and tungsten mineralization.

This study of the vein minerals indicates that groups of adjacent deposits have characteristic mineral assemblages distinguishing them from other groups; these form zones along the entire length of the belt. The following summarizes the principal mineralogical zones from west to east:: 1) pyrargyrite in quartz-siderite veins with some native silver, polybasite, stephanite, and acanthite are mainly in the west; 2) siderite, galena, sphalerite, and freibergite occur in most deposits but are found without the other index minerals on top of Galena Hill; 3) pyrrhotite and arsenopyrite are in deep vein exposures in the valley between Galena Hill and Keno Hill; 4) calcite is also in the deep veins along the eastern flank of Galena Hill but extends to the east onto Keno Hill; and 5) boulangerite-jamesonite and abundant quartz-arsenopyrite rich fractions of veins at the eastern end of the district overlap with the calcite zone. Higher gold values are recorded in zones 1, 2, and 5.

The changing mineralogical facies record an evolving environment of deposition in a continuous, 25 km long hydrothermal vein system. The western deposits are thought to be higher level, or laterally "downstream" equivalents of the eastern deposits.

This zoning sequence is typical and is well established in other regions of the world. Such systems are known to progress further downwards, into gold-quartz veins before attaining tin and tungsten mineralization and associated granitic bodies.

Authors: Lynch, G.

NTS Mapsheet(s): 105M

Citation: Lynch, G., 1986. Mineral zoning in the Keno Hill silver-lead-zinc mining district, Yukon. In: Yukon Geology Volume 1, J.A. Morin and D.S. Emond (eds.), Exploration & Geological Services Division, Indian & Northern Affairs Canada, p. 89-97.

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