The Macmillan Pass area has been of economic interest since the discovery of significant barite-lead-zinc-silver mineralization by Hudson Bay Exploration and Development prospectors in 1951. In addition to barite-hosted mineralization of the MacMillan Pass area, the Upper Devonian to Lower Mississippian "Black Clastic" Unit and its correlative rocks in southeast Yukon and northeast British Columbia contain perhaps the world's largest known accumulations of sedimentary barite.
TOM West Zone, TOM East Zone and JASON mineral deposits are syngenetic, stratiform accumulations principally composed of finely interlaminated barite, black siliceous argillite, sphalerite, galena and pyrite. The three deposits occur at approximately the same stratigraphic interval, marking the sedimentary transition between locally derived slump and slide debris deposits of Unit 3a with finer grained black shales and minor conglomerates of Unit 3b.
This Open File includes:: Regional Geology-Selwyn Mountains (1::263 157-scale bedrock map) and Geology of MacMillan Pass area, Yukon Territory (1::111 111-scale bedrock map with cross-section).