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The nature of the relatively shallow sub-surface was an important consideration for this study. Groundwater movement in this region is dominated by fracture flow. Fractures that were channelways for mineralizing fluids in the geologic past, and have been filled with both ore and gangue minerals, may have been reactivated in modern times and provided the foci for groundwater flow. Hence, fluids in the subsurface have encountered ore and gangue minerals that would contribute a number of trace elements to the fluids.

Mapping the distribution of subsurface fractures and recognizing zones of alteration at the local and regional scale was best achieved through geophysical techniques. High resolution (300 meter spacing) aeromagnetics and airborne electromagnetic methods were the requisite tools, proving almost continuous regional coverage, and the resolution was sufficient to evaluate fracture and alteration zone distribution at the local scale.

Further information on potential fields methods can be found at:http://crustal.usgs.gov/geophysics/

Aerial coverage of high-resolution aeromagnetics over study area. The southern coverage was flown in 1996 and the northern coverage in 1997.

Full resolution aeromagnetic image of study area.

For further information, contact Carol Finn.