Economic Prefeasibility Studies of Mining in the Koyukuk Mining District, Northern Alaska

Mining and processing cost analyses were conducted on nine mineral development scenarios for the Koyukuk Mining District study. The district is located on the upper portion of the Koyukuk River basin. Resources and recoverable metal values (RMV) needed to make these deposits yield a 15% Discounted Cash-Flow Rate-Of-Return (DCFROR) were modeled.

Economic modeling for surface-mined placer gold deposits indicated the RMV ranged from $18.43 per loose cubic yard (lcy) for a 243 loose cubic yards per day (lcy/d) operation to $4.23/lcy for a 1,941 lcy/d operation supported by a 10- mile (mi) road. The RMV ranged from $25.49/lcy for a 243 lcy/d operation to $4.84/lcy for a 1,941 lcy/d operation supported by a 50 mi road. The RMV ranged from $35.05/lcy for a 243 lcy/d operation to $5.63/lcy for a 1,941 lcy/d operation supported by a 100 mi road. The RMV ranged from $18.35/lcy for a 243 lcy/d operation to $4.62/lcy for a 1,941 lcy/d air supported operation approximately 200 mi from Fairbanks.

Modeling for surface-mined placer gold deposits indicated the RMV ranged from $16.82/lcy for a 243 lcy/d operation to $4.11/lcy for a 1,941 lcy/d operation supported by a 10 mi winter trail. The RMV ranged from $17.61/lcy for a 243 lcy/d operation to $4.18/lcy for a 1,941 lcy/d operation supported by a 50 mi winter trail. The RMV ranged from $18.55/lcy for a 243 lcy/d operation to $4.30/lcy for a 1,941 lcy/d operation supported by a 100 mi winter trail.

Modeling for underground-mined placer gold deposits indicated the RMV ranged from $19.73/lcy for a 243 lcy/d operation to $6.41/lcy for a 1,941 lcy/d operation supported by a 10 mi road. The RMV ranged from $26.82/lcy for a 243 lcy/d operation to $7.04/lcy for a 1,941 lcy/d operation supported by a 50 mi road. The RMV ranged from $36.04/lcy for a 243 lcy/d operation to $7.82/lcy for a 1,941 lcy/d operation supported by a 100 mi road. The RMV ranged from $18.19/lcy for a 243 lcy/d operation to $6.33/lcy for a 1,941 lcy/d air supported operation approximately 200 mi from Fairbanks.

Modeling for underground-mined placer gold deposits indicated the RMV ranged from $18.19/lcy for a 243 lcy/d operation to $6.28/lcy for a 1,941 lcy/d operation supported by a 10 mi winter trail. RMV ranged from $18.86/lcy for a 243 lcy/d operation to $6.37/lcy for a 1,941 lcy/d operation supported by a 50 mi winter trail. The RMV ranged from $19.99/lcy for a 243 lcy/d operation to $6.51/lcy for a 1,941 lcy/d operation supported by a 100 mi winter trail.

Modeling indicated that for an increment in RMV ranging from $2.18/lcy for a 243 lcy/d operation to $0.25/lcy for a 1,941 lcy/d operation, a backhoe and laborer can be added to the gold placer mine models.

Modeling for copper porphyry deposits indicated the RMV ranged from $90 per short ton (st) for a 3,913 short tons per day (stpd) operation to $37/st for a 31,309 stpd operation.

Modeling for copper skarn underground mines indicated the RMV ranged from $561/st for a 114 stpd operation to $299/st for a 912 stpd operation. Economic modeling for copper skarn surface mines indicated the RMV ranged from $455/st for a 114 stpd operation to $242/st for a 912 stpd operation.

Modeling for mineralized quartz vein deposits indicated the RMV ranged from $2,688/st for a 4 stpd operation to $538/st for a 36 stpd operation with an on-site mill. The RMV ranged from $1,596/st for a 4 stpd operation to $502/st for a 36 stpd operation which shipped ore directly to a smelter.

Modeling for massive sulfide deposits indicated the RMV ranged from $832/st for a 56 stpd operation to $368/st for a 452 stpd operation.