| Abstract |
Mineralization at the Win prospect was investigated by the Bureau of Mines in June, 1990 and 1991 as part of an ongoing investigation of the tin, niobium, and tantalum resource potential in Alaska. The Win prospect is located twenty miles northwest of McGrath, AK. Mineral deposits consist of polymetallic sulfide and quartz-cassiterite mineralized vein and breccia vein systems within a quartz-tourmaline (dravite)-altered hornfels aureole that appears to be related to a small dacite stock and dikes. Host rocks for most of the veins is altered, Late Cretaceous Kuskokwim Group flyschoid rocks. The dacite is a calc-alkalic, high Ca, low K, biotite, magnetite, garnet-bearing coarse-grained intrusive. Mafic and accessory mineral distribution in the stock and dikes is highly erratic. Veins and breccia veins often contain high tin and silver values (up to 18.82 oz/st Ag and 6.97% Sn over 7.75 ft), variable but significant amounts of copper, lead, zinc, arsenic, niobium, antimony, bismuth and tellurium, and trace amounts of gold, indium, and selenium. Mineralization is both distal and proximal to the dacite intrusive rocks, covering a roughly circular area 1.25 mi in diameter. Bedrock exposure of vein systems is limited and no resource is calculated. |
