In unconsolidated material, penetration rates for the all-terrain-vehicle (ATV) drill ranged from 3 ft/hr (0.9 m/hr) in frozen sandy pebble/cobble gravel to 33 ft/hr (10 m/hr) in unfrozen, loose muck. Drilling penetration was influenced by: 1) extent of freezing, 2) clast size, 3) distribution of clast size, and 4) degree of cohesiveness. Out of twenty-three holes, twelve reached bedrock and thirteen were gold-bearing. Maximum drill hole depth reached was 36 ft (11 m). Eleven holes were drilled adjacent to previously drilled larger diameter holes for gold value correlations. Six of these holes were known to be gold-bearing; our drilling indicated the presence of gold in five out of six holes. Small gold particles recovered from our drilling have a variety of shapes which range in size from 0.1 mm to 2 mm.
The ATV drill rig field tested in this study met most of the objectives of this project but gave mixed results. The ATV drill rig:
- is limited to terrain of relatively smooth microtopography
- is helicopter transportable but requires a medium sized helicopter
- can penetrate most surficial materials found in typical Klondike placer deposits except for coarse gravels and some frozen gravels
- is an acceptable tool for studying the general stratigraphy of Yukon placer deposits, although vertical sections are more representative of stratigraphy
- can detect the presence of gold in penetrable stratigraphy
- recovered gold from virtually every gold-bearing hole previously drilled by larger drill rigs but gold values were not as accurate as results from larger diameter drilling.
This particular ATV drill rig is limited by an old technological design and worn mechanical components which make it unsuitable for future projects of similar nature. However, the results of this project demonstrate that light weight and portable auger drilling has potential as a prospecting tool, particularly in drainage basins with limited geoscientific informaton and/or placer mining history.