Feasibility of Economic Zinc, Copper, Silver, and Gold Mining in the Porcupine Mining Area of the Juneau Mining District, Alaska.
The Bureau of Mines conducted studies to estimate mining costs in the Porcupine Mining Area of the Juneau Mining District, southeastern Alaska. Investigations were conducted on three mineral deposit types: (1) massive sulfide deposits containing zinc, copper, and silver, (2) vein gold, and (3) disseminated gold. Cost estimates were developed using the Bureau of Mines cost estimating system. Discounted cash flow rates of return were calculated using the Bureau of Mines minsim (mining simulation) computer program. Underground longhole stope mining of a massive sulfide deposit containing 25 pct zinc, 1 pct copper, and 68.6 G/mt silver was found to be economic at high metal prices at a quantity of 13,200,000 mt ore. Cut-and-fill mining of a 26,400,000 mt massive sulfide deposit was found to be economic at medium metal prices. Open pit mining of a similar deposit was found to be economic at medium metal prices and 26,400,000 mt ore, or at high metal prices and 6,600,000 mt ore. Underground mining of a vein gold deposit was found to be economic at a grade of 17.1 G/mt, medium metal prices, and 1,320,000 mt ore. Open pit mining of a disseminated gold deposit was found to be economic at a grade of 1.71 G/mt, medium metal prices, and a quantity of 39,600,000 mt ore.