This report documents the state of the Placer Mining Industry in the Yukon Territory for the 1993 and 1994 mining seasons. This report differs from previous volumes in that the placer mining inspection reports are organized by drainage basin. The majority of this volume consists of detailed descriptions of placer operations visited by the staff of the Placer Mining Section of the Mineral Development Division, Northern Affairs Program, Yukon Region. Also included is information that may be useful to readers who are interested in searching for and developing placer properties in the Yukon Territory. This volume contains four papers of general interest: "Prehistoric gold" describes the discovery of an extinct Ice Age horse; "Water" is a brief account that tells of the difficulties, historically, in obtaining water for placer mining; "Oldest valid Yukon placer claims" describes claims kept in good standing for the greatest length of time; and "The early development of placer mining in the Yukon 1873-1896" is a historical overview of the development of placer mining in the Yukon.

This project was undertaken to evaluate the potential to economically recover additional metal values from the 4.6 million tons of Keno Hill flotation tailings which grades 3-4 oz/t silver, 0.8% lead and 0.9% zinc. The study determined that the higher grade portion of the tailing, containing some 1.0 million tons at 5.35 oz/t Ag, responds well to cyanide heap leaching with a silver recovery of 50-60%. The testing data suggests that heap leaching is economically feasible at the current silver price of $US5.50/ounce and a currency exchange rate of 1.35 in favour of the US dollar. The response to gravity and flotation concentration was poor.

Diamond placer occurrences are historically reported in Yukon and in the adjacent areas of British Columbia and Alaska (Casselman and Harris, 2002) and are generally recovered during clean-ups on placer gold mining operations. While three stones from Crooked Creek in Alaska have been scientifically confirmed and described (Forbes et al., 1987), the same cannot be said of the Yukon diamond placer occurrences. In the Yukon, reports of a diamond discovery initiated sampling for diamond-indicator minerals that subsequently returned neither diamonds nor their indicators (chrome-diopside, pyrope-garnet, picro-ilmenite). Furthermore, none of the known ultramafic rocks, diatremes of ultramafic-alkaline volcanic rocks nor high-pressure eclogites in Yukon and Alaska have been proven to be diamond-bearing. Alluvial diamonds are present along the West Coast in Oregon and California (Hausel, 1994) and exploration of diamond placers in California produced several hundred stones, including high-quality gems. However, all of these aforementioned occurrences lack diamond-indicator minerals common for cratonic diamond deposits, and no igneous diamond-bearing rocks are known in the area. Therefore, the placer occurrence of diamonds in Yukon as well the Pacific Coast remains enigmatic.

The core of Glenlyon and northeastern Carmacks map areas is underlain by a northwest-trending belt of metasedimentary, metavolcanic and (meta)plutonic rocks of the Yukon-Tanana Terrane. It includes two successions of Carboniferous arc volcanic rocks, associated plutonic suites of Mississippian age, Devonian-Mississippian metaclastic rocks, and their basement complex. To the southwest, Yukon-Tanana Terrane is juxtaposed with the Semenof block a belt of mafic metavolcanic rocks of uncertain terrane affinity along the Needlerock and Big Salmon faults. To the northeast, the Tummel fault zone delineates the contact between Yukon-Tanana and Cassiar terranes. The narrow belt of chert, argillite and greenstone which occurs within the Tummel fault zone probably correlates with the Slide Mountain Terrane. The area is intruded by Early Jurassic and Cretaceous plutons and is dissected by a series of late faults, which results in approximately 56 km of dextral offset of the Yukon-Tanana Terrane.