Abstract: The physiography and glacial history of Yukon bear directly on the geological setting, grade and economic viability of Yukon placer deposits. The limits of several advances of the Cordilleran Ice Sheet are evident in south central Yukon in the form of deposits and ice-marginal features left successively southeast by retreat of the three main glacial episodes.

The oldest, including multiple glaciations, was the pre-Reid at up to 3 Ma, succeeded by the Reid at up to 200 Ka, and the McConnell which ended approximately 10.3 Ka.

Yukon placer deposits are grouped into five broad categories based on age, gemorphic and sedimentologic characteristics. These are 1) Pliocene to early Pleistocene alluvial placer deposits preserved as high level terraces buried beneath non-auriferous overburden; 2) Pleistocene non-glacial alluvial placer deposits that occur as valley-bottom fill and low to high level terraces in unglaciated terrain; 3) Interglacial placer deposits that occur as valley-bottom alluvial fill or low terraces in drainages that have escaped the effects of glacial erosion; 4) Glacial placer deposits that have formed when gold from regional bedrock or paleoplacer sources was incorporated into glacial drift; and 5) Recent placer deposits that are found as colluvial deposits, valley-bottom alluvial blankets in gulches and tributary valleys, bar deposits in major river systems and beach and nearshore marine deposits.

Ten major regions produce placer gold in Yukon:: Indian River; Klondike; west Yukon (Sixtymile/Fortymile/Moosehorn); Lower Stewart; Clear Creek; Mayo; Dawson Range; Kluane; Livingstone and Whitehorse South. Since 1886, these areas have produced over 15 million crude ounces of placer gold, mainly from the unglaciated Klondike, west Yukon and Lower Stewart regions.

Many areas in Yukon remain unexplored for new placer gold deposits, both in unglaciated and glaciated areas. Areas of exploration potental in unglaciated areas include abandoned channels, oxbows and point bars, high level terraces, and tributary gulch and creek placers. In and along the margins of glaciated areas, pre-glacial or interglacial placer deposits may lie buried by glacial and glaciofluvial drift. Lower-grade placer deposits may have formed by glaciofluvial reworking of pre-glacial or interglacial placers. Non-glacial placer deposits may be found unconformably overlying glacial drift. Deeply incised interglacial valleys oriented obliquely to paleo-ice flow directions are also favourable locations for the preservation of economic placer deposits in glaciated areas.

Interest in exploring for new gold reserves has been sparked by new placer research and surficial mapping programs initiatied by the Yukon Geology Program and the Geological Survey of Canada. As this research continues to add to the understanding of placer gold deposits, exploration activity is expected to continue and new reserves in both unglaciated and glaciated areas may be found.

Authors: LeBarge, W.P.

Map Scale: 1 : 0

Citation: LeBarge, W.P., 1997. Overview of Yukon placer geology, gold production and prospects. In: Yukon Quaternary Geology Vol. 2, W.P. LeBarge and C.F. Roots (eds.) 1997, Indian & Northern Affairs Canada/Department of Indian & Northern Development: Exploration & Geological Services Division, p. 1-9.